John Randall and Chloe Smith quit government posts
Two Conservative members of the government have quit amid speculation of an imminent ministerial reshuffle.
Deputy Chief Whip John Randall and Cabinet Office Minister Chloe Smith stepped down late on Sunday.
Mr Randall, 58, has been Conservative MP for Uxbridge and South Ruislip since 1997, while Chloe Smith has represented Norwich North since 2009.
BBC political editor Nick Robinson said a government reshuffle could take place as soon as Monday.
He said it was likely to focus on "mid-ranking ministers below cabinet level".
As Deputy Chief Whip, Mr Randall was partly responsible for ensuring party discipline among fellow Tory MPs.
He offered to quit at the end of last year, his resignation letter said.
Ms Smith, 31, served in the Treasury before being moved to the Cabinet Office last September.
Stepping down, she wrote to the prime minister pointing out she had been "only 27" when she became an MP and said she now wanted to "develop other ways of giving public service".
She was thrust into the limelight last summer when she appeared on BBC Two's Newsnight to defend the government's fuel duty policy.
The widely viewed interview with Jeremy Paxman prompted one Tory MP to label Chancellor George Osborne a "coward" for putting her forward in his place.
Mr Randall had worked in the whips' office, either in government or opposition, for 13 years.
In his resignation letter he paid tribute to David Cameron and said it had been "a great privilege and honour" to serve the party.
The departures come after Transport Minister Simon Burns quit his post on Friday to launch a bid to become a deputy Speaker.
Our political editor said: "The prime minister is known to be keen to promote women and those representing northern constituencies ahead of the general election and a wider Cabinet reshuffle which may take place next spring."
BBC political correspondent Vicky Young says the Tories have a lot of talented women in junior roles who could be candidates for promotion.
It is thought that Deputy Prime Minister Nick Clegg will also make changes to the Liberal Democrat ministerial line-up and Labour leader Ed Miliband is expected to reshuffle his shadow ministerial team.