A row has broken out over the date of Oldham East and Saddleworth by-election, with Labour accusing the coalition of "running scared" of student voters.
By holding the poll on 13 January, Labour said nearly a thousand students may be unable to vote.
Ministers said it was "astonishing" that Labour did not want the poll to take place as soon as possible.
Campaigning has got under way after the writ was formally moved on Thursday.
The by-election was triggered by a court decision annulling former Labour minister Phil Woolas's victory in May, by 103 votes from the Liberal Democrats, and banning him from politics for three years.
Labour have expressed anger at the shortness of the campaign which will be truncated by the Christmas and New Year holidays.
In Parliament, Shadow Leader of the Commons Hilary Benn suggested the date had been chosen to favour the Liberal Democrats as it meant that nearly 1,000 students would not have returned to colleges in the constituency by that date and were "likely to be disenfranchised".
The Lib Dems have been the focus of student anger after Parliament's decision to increase tuition fees in England and Wales to a maximum of £9,000 - in direct contradiction to a pre-election pledge by their MPs to oppose higher fees.
Arguing for the poll to be held on 3 February instead, Mr Benn said: ""Does this not just show that the coalition is running scared of the judgement of students at the ballot box?"
Commons leader Sir George Young said his counterpart's comments were a "bit rich" since Labour had not opposed the writ being moved for the by-election - the parliamentary method for agreeing the poll - earlier in the Commons on Thursday.
He denied there had been a "break with convention" in allowing the Lib Dems - rather than Labour - to move the writ. It is customary practice for the party which previously held the seat to move the writ.
"It is astonishing they [Labour] do not want this by-election to be held when their own candidate said 'I can't wait until polling day'. So what is the fuss all about?," Sir George said.
He also told MPs that no-one had been disenfranchised by the choice of date for the vote.
A Lib Dem spokesman said: "This is another sign that Labour just don't understand the constituency. With polling day outside of term time, there will actually be many more students at home in Oldham, than would otherwise have been the case."
Labour leader Ed Miliband and senior Lib Dems are set to visit the constituency as parties step up their efforts. Prime Minister David Cameron is also expected to visit during the course of the campaign.
The by-election will be watched carefully as it will be highest profile vote since the coalition government was formed in May.
Labour beat the Liberal Democrats by just 103 votes in May's contest, with the Conservatives in third place.
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.