The Act provided for 128 MPs elected from 28 constituencies for the House of Commons of Southern Ireland. Only the Dublin University MPs attended for the intended first meeting of the House of Commons of Southern Ireland, with those elected for Sinn Féin sitting as TDs in Dáil Éireann. The members elected for Southern Ireland did meet to give legal effect to the Anglo-Irish Treaty.
Westminster House of Commons
The Government of Ireland Act reduced the representation from Ireland in the United Kingdom House of Commons from 105 to 46. Of these, 33 were to be elected from constituencies in Southern Ireland and 13 from constituencies in Northern Ireland. Each six-, seven- and eight-member constituency would also be a two-member constituency for the Westminster, while every three-, four- and five-member constituency would be a one-member constituency for Westminster. As the Irish Free State was due to be established on 6 December 1922, just after 1922 general election, the representation at Westminster under this Act only took effect in Northern Ireland.
Dáil Éireann
The First Dáil had used the constituencies which elected MPs to the House of Commons at the 1918 general election. In May 1921, Dáil Éireann resolved to use the constituencies in the Government of Ireland Act 1920. The 1921 elections were used to elect the Second Dáil. This increased the total number of seats in the Dáil from 105 in 1918 to 180 in 1921. Only representatives from Sinn Féin sat in the Dáil. The Third Dáil redistributed constituencies in the Irish Free State by enacting the Electoral Act 1923. The new constituencies were used to elect the members of the 4th Dáil at the 1923 general election.
Constituencies
Northern Ireland
Belfast
1918 Act: 9 MPs 1920 Act: 16 MPs in NIHC & 4 MPs in UKHC !colspan=3| Boroughs !1918 Act!!Change!!1920 Act The East Belfast constituency consisted of the Pottinger and Victoria divisions The North Belfast constituency consisted of the Duncairn and Shankill divisions The South Belfast constituency consisted of the Cromac and Ormeau divisions The West Belfast constituency consisted of the Falls, St Anne's and Woodvale divisions
Antrim
1918 Act: 4 MPs 1920 Act: 7 MPs in NIHC & 2 MPs in UKHC !colspan=3| Counties !1918 Act!!Change!!1920 Act
Armagh
1918 Act: 3 MPs 1920 Act: 4 MPs in NIHC & 1 MP in UKHC !colspan=3| Counties !1918 Act!!Change!!1920 Act
Down
1918 Act: 5 MPs 1920 Act: 8 MPs in NIHC & 2 MPs in UKHC !colspan=3| Counties !1918 Act!!Change!!1920 Act
Fermanagh and Tyrone
1918 Act: 5 MPs 1920 Act: 8 MPs in NIHC & 2 MPs in UKHC !colspan=3| Counties !1918 Act!!Change!!1920 Act
Londonderry
1918 Act: 3 MPs 1920 Act: 5 MPs in NIHC & 1 MP in UKHC !colspan=3| Counties !1918 Act!!Change!!1920 Act
Universities
1918 Act: 1 MPs 1920 Act: 4 MPs in NIHC & 1 MP in UKHC !1918 Act!!Change!!1920 Act
Southern Ireland
Ulster (part)
Representation increased from 8 to 12 MPs !colspan=3| Counties !1918 Act!!Change!!1920 Act
Leinster
Representation increased from 27 to 44 MPs !colspan=3| Boroughs !1918 Act!!Change!!1920 Act The Mid Dublin constituency consisted of the College Green and Dublin Harbour divisions The North West Dublin constituency consisted of the Clontarf, St James's and St Michan's divisions The South City constituency consisted of the St Patrick's and St Stephen's Green divisions !colspan=3| Counties !1918 Act!!Change!!1920 Act
Munster
Representation increased from 24 to 40 MPs !colspan=3| Boroughs !1918 Act!!Change!!1920 Act !colspan=3| Counties !1918 Act!!Change!!1920 Act
Connacht
Representation increased from 13 to 24 MPs !colspan=3| Counties !1918 Act!!Change!!1920 Act
Universities
Representation increased from 3 to 8 MPs !1918 Act!!Change!!1920 Act
