Former chief secretary to the Treasury David Laws has played down talk of an early return to the cabinet.
He told the BBC the standards inquiry into his expenses claims - the reason he quit his post in the summer - could "take some time".
And he said he was focusing on lobbying ministers over the pupil premium and "policies that I'm passionate about".
Mr Laws paid tribute to his successor, Danny Alexander, adding: "I don't think they've missed me since I've left."
Mr Laws resigned from the cabinet in May after just 16 days as chief secretary to the Treasury, following reports he had claimed expenses to pay rent to his partner, the lobbyist James Lundie, and referred his case to the parliamentary standards commissioner.
Since he left there has been much speculation he might return to cabinet if cleared. But he told BBC Radio 4's Westminster Hour that the inquiry could take some time.
"It's not possible to anticipate the dates on these things. The usual process does take some time because there is a process to be observed so I don't think there is a date yet," he said.
'Damned good ministers'
'I am focusing on the very big job that I've got, I am doing my best to lobby my party leader and my colleagues in government about the policies that I'm passionate about, particularly things like the pupil premium and it's those things that I'm really in politics to deliver.
"And we've got damn good ministers, including Danny Alexander, who are doing a very good job in the Treasury and I don't think that they've missed me since I've left."
In May the Telegraph reported that between 2004 and 2007, Mr Laws had claimed between £700 and £950 a month - about £40,000 in total - to sub-let a room in a flat in Kennington, south London, from Mr Lundie.
Since 2006, parliamentary rules had banned MPs from "leasing accommodation from a partner" but Mr Laws said he had wanted to keep his relationship with Mr Lundie private.
He told the programme: "It was obviously very difficult indeed for all the reasons that people will understand, but there are lots of people who deal with tough circumstances in their life and the job is one that is very important to me and constituents have been very generous in their support and their encouragement."
'Unwilling to concede'
Mr Laws, who was a key member of the Lib Dem negotiating team in the days after the general election resulted in a hung parliament, said former Lib Dem leaders "would have given their right arm" to enter coalition with Labour.
But he said Labour had been "ill-prepared and unwilling to make concessions to us".
He added that the party would have to engage with the Lib Dems "in a more constructive way and a more serious way in the future, if they have to have any chance of having a proper relationship with the Liberal Democrat party."
In October Mr Laws hinted that he hoped to return to government, telling the BBC: "Everybody wants to be in the front line".
David Laws' interview with The Westminster Hour will be broadcast on BBC Radio 4 on Sunday at 2200 GMT.