It was triggered when Elwyn Jones, the constituency's Labour Party Member of Parliament (MP), was appointed as Lord Chancellor and subsequently awarded a life peerage.

Given that there was a hung parliament, and at the time of the by-election a general election was thought likely, any changes in the share of the vote between the main parties could have given a guide as to the likely future government.

Jones had won a majority of more than 50%,[1] and had held the predecessor seat of West Ham South since its creation at the 1950 general election.

Labour chose Nigel Spearing as its candidate; previously the MP for Acton, he had lost his seat at the February election.

The Liberals, Conservatives and National Front all fielded the same candidates who had stood in February, hoping to build on their performance.