The Labour Party was accused of hypocrisy last night after it criticised Alex Salmond for his dual role as MP and MSP.

Harriet Harman, the party's deputy leader, condemned the Scottish First Minister's low attendance in the Commons even though the Labour candidate in the Glasgow East by-election would, if successful in becoming an MP, retain her status as an MSP.

Ms Harman was standing in for Gordon Brown at Prime Minister's questions in the Commons. In criticising the SNP leader's dual mandate, she said: “The leader of the Scots Nats in Holyrood doesn't turn up much in this House although he continues to be a member and draw his salary.”

Ms Harman's attack on Mr Salmond's two roles only served to increase the pressure on Margaret Curran, Labour's by-election candidate, who is at present an MSP and wants to serve in both parliaments in the “short term”.

Annabel Goldie, the Scottish Tory leader, accused Labour of being in chaos. She said: “Harriet Harman says you cannot be an MP and an MSP at the same time, whilst her own candidate in Glasgow East has refused to pledge to stand down as an MSP if she wins. This is either hypocrisy or ignorance, and neither is a virtue. The voters of Glasgow East deserve a full-time MP. After all, that's what you're paid to be.”

Ms Harman's remarks backfired, coming just a day after her own party accused John Mason, the SNP candidate in the by-election of ‘breathtaking hypocrisy' after he suggested that Ms Curran was wrong to try to hold on to her job as an MSP instead of concentrating on her MP role full-time in the event she is elected.

Although Mr Salmond is at present the only Scottish politician to hold a dual mandate, the SNP is still keen to make the two jobs question a dominant one in the by-election. SNP strategists believe that the First Minister won his argument to carry out both roles when he stood in the Scottish Parliament elections last year and that Ms Curran will find it a more difficult issue to sell in the east end of Glasgow where almost 50 per cent of the electorate do not hold one job.

The SNP said: “Alex Salmond made his position clear and won his elections, and John Mason has made his position clear and upfront. Margaret Curran is the person with all the questions to answer.”

Labour said that Ms Curran's position could not be compared to that of Mr Salmond: “Margaret's entire Scottish Parliament seat is within the constituency she is standing for, she would work out of one office and she would not be attempting to carry out the job of First Minister as well. The situations are totally different.”

As nominations for candidates in the by-election closed last night, Nick Clegg, the Liberal Democrat leader, called on David Cameron, the Tory leader, to apologise to the people of Glasgow East for implying that it was their own fault they were poor.

Mr Clegg said: “If David Cameron has any decency he would apologise to the people of Glasgow East for the arrogance of his comments.”

In a speech in Glasgow East Mr Cameron claimed that politicians were too afraid to say what was right and wrong: “We talk about people being at risk of obesity, instead of talking about people who eat too much and take too little exercise. We talk about people being at risk of poverty or social exclusion. It's as if these things, obesity, alcohol abuse, drug addiction, are purely external events like a plague or bad weather.” The comments infuriated Mr Clegg, who interpreted them as an attack on the poor.

The candidates

Chris Creighton Independent

Frances Curran

Scottish Socialist Party

Margaret Curran

Scottish Labour Party

Eileen Duke Scottish Green Party

Hamish Howitt Freedom-4-Choice John Mason

Scottish National Party

Tricia McLeish Solidarity

Davena Rankin

Scottish Conservatives

Ian Robertson

Scottish Liberal Democrats

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