The issue of Ireland has been a major one in British politics, intermittently so for centuries. Britain's attempts to control and administer the island, or parts thereof, have had significant consequences for British politics, especially in the 19th and 20th centuries. Although nominally autonomous (as the Kingdom of Ireland) until the end of the 18th century, Ireland became part of the United Kingdom of Great Britain and Ireland in 1801.

In 1844, a future British prime minister, Benjamin Disraeli, defined what he called the Irish Question:

The Great Famine of 1845–1851 killed upward of 1 million Irish men, women, and children, and forced another million to migrate, especially to the United States. Poor handling by the British government left distrust and hatred in its wake, roiling every grievance that followed. The view in Ireland was that the combination of laissez faire policies, which permitted food exports from Ireland, and protectionist Corn Laws, which prevented import of low cost wheat, had been a major factor in the famine, and that an independent government would have mitigated it.

The Representation of the People Act 1884 enfranchised many Catholics in Ireland. Charles Stewart Parnell mobilised the Catholic vote so that the Irish Parliamentary Party held the balance of power in the Parliament of the United Kingdom. Parnell sought to re-establish home rule for Ireland and used tactics that kept British politics in turmoil. William Gladstone and the Liberal Party usually worked with Parnell in search of Home Rule, but the Liberal Party was irreversibly split in doing so, and a substantial faction left to form the Liberal Unionist Party. The result was the long-term decline of the Liberal Party.

Home Rule was passed in 1914, but suspended in operation during the First World War. The issue was resolved in 1921 by partitioning Ireland into the quasi-autonomous, Catholic-dominated, Irish Free State in the southwestern four-fifths of the island, and the Presbyterian dominated Northern Ireland in the remaining fifth, which remained part of the United Kingdom.A short summary see Nick Pelling, Anglo-Irish Relations, 1798–1922 (2003) The next round of troubles emerged in the 1960s, when the Catholics living in Northern Ireland could no longer tolerate the discriminatory policies long imposed on them by the devolved government of Northern Ireland. The Troubles 30 years of near civil war which had sporadic but significant impact on British politics ended with the Good Friday Agreement of 1998, a power-sharing agreement between the parties in Northern Ireland and an international treaty between Ireland and the United Kingdom, as co-guarantors.

From 2017 onwards, Britain's relationship with Ireland again disrupted British politics, specifically over Brexit. Until late 2019, Parliament was unable resolve the trilemma among three competing objectives: an open border on the island; no trade borders within the United Kingdom; and no British participation in the European Single Market and the European Union Customs Union. The government abandoned the second of these objectives by negotiating and signing the Northern Ireland protocol that took effect from early 2021.

18th century For most of the 18th century, Ireland was largely quiet, and played a minor role in British politics. Between 1778 and 1793, nearly all the laws restricting Catholics in terms of worship, owning or leasing lands, education, and entry into the professions were repealed. Wealthy Irish Catholics attained the franchise in 1793. The main remaining restriction was the prohibition against Catholics sitting in Parliament. Prime Minister William Pitt the Younger took an active role in the reforms. King George III, a staunch Protestant, was troubled by the reforms. He balked at Catholic membership in Parliament, forcing Pitt to resign in 1801.G. M. Ditchfield, "Ecclesiastical Legislation During the Ministry of the Younger Pitt, 1783–1801." Parliamentary History 19.1 (2000): 64–80.

Although the Catholic majority was regaining its rights, Ireland's economy, politics, society, and culture were largely dominated by the Anglican landowners, who comprised the Protestant Ascendancy. There was a large Presbyterian ("Non-conformist") population in the north-east, who resented being pushed to the margins by the Anglican established church. They took the lead in cultivating Irish nationalism after 1790.

1798 Rebellion

The 1798 Rebellion was a major uprising against British rule in Ireland. The main organising force was the Society of United Irishmen, a republican revolutionary group influenced by the ideas of the American and French revolutions: originally formed by Presbyterian radicals angry at being shut out of power by the Anglican establishment, they were joined by many from the majority Catholic population.

Following some initial successes, particularly in County Wexford, the uprising was suppressed by government militia and yeomanry forces, reinforced by units of the British Army, with a civilian and combatant death toll estimated between 10,000 and 50,000. A French expeditionary force landed in County Mayo in August in support of the rebels: despite victory at Castlebar, they were also eventually defeated. The aftermath of the Rebellion led to the passage of the Acts of Union 1800, merging the Parliament of Ireland into the Parliament of the United Kingdom.

Early 19th century

The agreement which led to the Act of Union stipulated Catholic emancipation and repeal of the Penal Laws in Ireland. However, King George III blocked Catholic emancipation, citing his coronation oath to defend the Anglican Church. A campaign under Roman Catholic lawyer Daniel O'Connell led to Catholic emancipation in 1829, allowing Catholics to sit in Parliament. O'Connell then mounted an unsuccessful campaign for the Repeal of the Acts of Union.

Great Famine

When a potato blight struck Ireland in 1846, much of the peasant population lost their staple food, as cash crops were reserved for export to Great Britain.Christine Kinealy, This Great Calamity: The Irish Famine 1845–52, Dublin: Gill & Macmillan, 1994. p354Cecil Woodham-Smith, The Great Hunger: Ireland 1845–1849 (1962), p 31 While large sums for relief were raised by private individuals and charities, inadequate action by the government, which believed in laissez-faire policies, and the protectionist Corn Laws, which made wheat unaffordable, led the problem to metastasize into a catastrophe. The class of cottiers, or farm labourers, was virtually wiped out through death and emigration, in what became known in Britain as 'The Irish Potato Famine' and in Ireland as the Great Hunger.

The famine and its memory permanently changed the island's demographic, political, and cultural landscape. Those who stayed and those who left never forgot. The mishandling of the famine became a rallying point for Irish nationalist movements. The already acerbic relations between Irish Catholics and the British Crown soured further, heightening ethnic and sectarian tensions. Republicanism became a factor.Nick Pelling, Anglo-Irish Relations, 1798–1922 (2003) pp 41–58

1868 to 1900 Church of Ireland The first premiership of Benjamin Disraeli in 1868 was short and was dominated by the heated debate over the Church of Ireland, a Protestant church associated with the Anglican Church of England. Although Ireland was three-fourths Roman Catholic and 90% nonconformist, the Church of Ireland remained the established church and was funded by tithes (direct taxation). The Catholics and the Presbyterians resented that fact.Allen Warren, "Disraeli, the Conservatives and the National Church, 1837–1881." Parliamentary History 19.1 (2000): 96–117. online The Irish Church was eventually disestablished by Gladstone's Irish Church Act 1869, causing divisions among the Conservatives.Robert Blake, Disraeli (1967), pp. 496–499.

Home Rule movement

Most (registered, land-owning male) Irish people elected as their MPs, Liberals and Conservatives who belonged to the main British political parties. A significant minority also elected Unionists, who championed maintenance of the Union and opposed Home Rule. A former Tory barrister turned nationalist campaigner, Isaac Butt, established a new moderate nationalist movement, the Home Rule League, in the 1870s. After Butt's death the Home Rule Movement, or the Irish Parliamentary Party as it had become known, turned into a major political force under the guidance of William Shaw and in particular Charles Stewart Parnell. Born into a wealthy and powerful Anglo-Irish Anglican landowning family, he entered the House of Commons in 1875. He was a land reform agitator, and became leader of the Home Rule League in 1880. Parnell operated independently of the Liberals, and won great influence by his balancing of constitutional, radical, and economic issues, and by his skillful use of parliamentary procedure. His party fillibustered the Protection of Persons and Property Act 1881 for seven weeks until the Speaker made a very rare change to British constitutional convention to close a debate after the IPP halted all progress on a Government Bill for five days in a row. (Op-ed) He was interned in Kilmainham Gaol in 1882 under the new Act but, as a very capable negotiator, was released when he renounced violent extra-Parliamentary action in exchange for repeal of the Act; in response, William Edward Forster resigned as Chief Secretary for Ireland, as did the Lord Lieutenant, John Spencer, 5th Earl Spencer.

Balance of power

From 1885 to 1915, the Irish Parliamentary Party led by Parnell frequently held the balance of power at Westminster between the Liberal and Conservative parties and used it to extract concessions for Ireland. The Conservative minority government of Lord Salisbury enacted the Purchase of Land (Ireland) Act 1885 ("Ashbourne Act") in return for the support of the Irish Parliamentary Party.

Parnell's movement campaigned for "Home Rule," by which Ireland would govern itself in domestic affairs inside the United Kingdom, in contrast to O'Connell who wanted complete independence subject to a shared monarch and Crown. Two Home Rule Bills (1886 and 1893) were introduced by Liberal Prime Minister Ewart Gladstone, but neither became law, mainly due to opposition from the House of Lords. The issue divided Ireland, for a significant unionist minority (largely based in Ulster), opposed Home Rule, fearing that a Catholic-Nationalist parliament in Dublin would mean rule by Rome and a degradation of Protestantism. To them, it also portended economic stagnation by Catholic peasants who would discriminate against businessmen and would impose tariffs on industry, which was located mostly in Ulster. Joseph Hocking, for example, warned that "history teaches that Rome Rule means corruption, decadence, and ruin."Joseph Hocking, Is Home rule Rome rule? (London, 1912) p 8.online The last phase of Gladstone's career was devoted to the Irish question.Nick Pelling, Anglo-Irish Relations, 1798–1922 (2003) pp 59–78 He sought repeatedly to pass a home rule bill but failed in 1886 and again in 1893.

Liberal Party split

In 1886, the ruling Liberal Party split over Gladstone's Home Rule proposals. Some Liberals believed that Gladstone's Home Rule bill would lead to eventual independence for Ireland and the dissolution of the United Kingdom of Great Britain and Ireland, a prospect which they could not accept. Seeing themselves as defenders of the Union, they called themselves "Liberal Unionists", although at this stage most of them did not think the split from their former colleagues would be permanent. In reality, they first supported then in time merged with the Conservative Party, to create the Conservative and Unionist Party. The Liberal Party, which had ruled Britain for generations, became in time a shadow of its former self.

Fenianism