The Liberal Democrats have called on First Minister Alex Salmond to quit his Westminster seat.
Mr Salmond holds seats in both the Scottish and UK Parliaments
It comes on the 100th day since Alex Salmond last spoke in the Commons.
Earlier this week, he promised to keep a pledge to collect one salary after it emerged he had still been receiving both his MP's and MSP's salaries.
Deputy First Minister Nicola Sturgeon has defended Mr Salmond, accusing the Liberal Democrats of "hypocrisy" and "mischief-making".
Mr Salmond has not made an appearance in London since the Scottish National Party won the Holyrood elections in May.
The Lib Dem's Scotland spokesman, Alistair Carmichael, said he believed Mr Salmond's constituents in Banff and Buchan had lost their MP and the first minister should resign his seat.
Mr Salmond's office insist both sets of constituents knew his intention was to become first minister, which it said is his priority.
Mr Salmond has said he will only draw his Westminster salary and will pay back the money he has received from the Scottish Parliament since he was elected as an MSP in May.
Ms Sturgeon described Mr Salmond as a "first-class MP" and hit back at the Lib Dems' comments.
She said: "This is mischief-making by the Liberal Democrats, but more than that, it is hypocrisy.
"Alex is, of course, following the precedent set by Jim Wallace when he became deputy first minister some years ago."