|October 1974–1979 Parliament|
These representative diagrams show the composition of the parties in the 1983 general election.
Note: The Scottish National Party and Plaid Cymru sit together as a party group, while Sinn Féin has not taken its seats. This is not the official seating plan of the House of Commons, which has five rows of benches on each side, with the government party to the right of the Speaker and opposition parties to the left, but with room for only around two-thirds of MPs to sit at any one time.
|SDP–Liberal Alliance||23 (6 + 17)|
|Ulster Unionist Party||11|
|Democratic Unionist Party||3|
|Scottish National Party||2|
|Social Democratic and Labour Party||1|
|Ulster Popular Unionist Party||1|
|Notional Government Majority||144|
|Effective Government Majority||151|
See the list of United Kingdom by-elections.
Two seats were vacant when Parliament was dissolved preparatory to the 1987 general election:
- Kirkcaldy – Harry Gourlay (Lab) died 20 April 1987
- Lewisham, Deptford – John Silkin (Lab) died 26 April 1987