The party is defending a majority of 13,507 in the seat in its traditional Scottish heartlands.

The rising cost of living - in particular, fuel, energy and food prices - have loomed large over the campaign.

Scotland's First Minister Alex Salmond has claimed it is the first by-election for 20 years where the cost of living has been a dominant issue.

And right from the start he said his party was set to pull off a "political earthquake".

The Scottish National Party would need a swing of 22% to achieve that - but if they did the result would raise questions over the future of Prime Minister Gordon Brown.

The by-election in Glasgow East was triggered by the resignation on health grounds of sitting Labour MP David Marshall.

Labour's Margaret Curran, a former Holyrood minister who represents part of the area as an MSP, is up against the SNP's John Mason, a Glasgow councillor.

In all, nine candidates are contesting the Glasgow East by-election.

They are: Davena Rankin (Conservative); Margaret Curran (Labour); Ian Robertson (Liberal Democrat); John Mason (Scottish National Party); Eileen Duke (Green); Hamish Howitt (Freedom-4-Choice); Chris Creighton (Independent); Tricia McLeish (Solidarity), and Frances Curran (Scottish Socialist Party).