Oldham East by-election to be held on 13 January
The Oldham East and Saddleworth by-election will be held on 13 January.
The writ for the by-election, which will be the first to be held since May's general election, will be moved in Parliament on Thursday.
The by-election was triggered by a court decision annulling Phil Woolas' victory in May and banning him from politics for three years.
Labour beat the Liberal Democrats by 103 votes in May's contest.
However, a specially convened election court threw out the result after it found that Mr Woolas had made misleading statements about his Lib Dem opponent.
Mr Woolas challenged the verdict, with an announcement about a by-election date delayed until he recently gave up legal proceedings.
Labour have expressed anger at the shortness of the campaign which will be truncated by the Christmas and New Year holidays.
The opposition can oppose the writ when it is moved but if they were to succeed in voting it down, it would not be moved again this session - leaving the constituency without an MP for more than a year.
Asked about the issue at prime minister's questions on Wednesday, David Cameron accused Labour of "running scared" over the prospect of a by-election.
The by-election will be the first significant electoral test for the coalition since it was formed in May.
The BBC's Political Correspondent Gary O'Donoghue said the Lib Dems wanted to get the campaign under way quickly but Labour were unhappy about campaigning over the festive period.
The Conservatives and the Liberal Democrats have chosen the same contenders - Kashif Ali and Elwyn Watkins - who represented them earlier this year.
Labour have selected Debbie Abrahams, who came third in the Colne Valley constituency in May.
UKIP chairman Paul Nuttall and BNP leader Nick Griffin also plan to stand.