Baroness Warsi has been removed from her role as Conservative Party co-chairman in David Cameron's first major reshuffle of the coalition Government.
Lady Warsi had appealed to the Prime Minister to allow her to carry on in the post but she was widely expected to be moved on.
Her deputy, Michael Fallon, housing minister Grant Shapps and employment minister Chris Grayling are seen as strong candidates to take over.
The peer used her official @ToryChairman Twitter account this morning to confirm she was "signing off", saying it had been "a privilege and an honour to serve my party as co-chairman".
Ken Clarke has agreed to leave his role as Justice Secretary but is likely to remain in the Government, the BBC reported.
Another minister who appeared to be among the casualties was Cheryl Gillan, who has removed references to her role as Welsh Secretary from her biographical details on Twitter.
The first confirmed appointment of the reshuffle was Andrew Mitchell as the new chief whip - a move confirmed late on Monday night. Mr Mitchell leaves his post as Secretary of State for International Development to replace Patrick McLoughlin, who is expected to be given a new job, in the key enforcer role for a Tory Party that has become increasingly rebellious.
Mr Cameron used his more discreet Commons office rather than No 10 to begin talking to the Government's most senior members on Monday night.
The reshuffle is expected to see ministerial jobs given to a raft of new faces from the 2010 intake as Mr Cameron attempts to build the team he wants around him in the run-up to the next general election.
Former Liberal Democrat Treasury minister David Laws is predicted to make a return to the front benches, while key figures such as Chancellor George Osborne and Foreign Secretary William Hague are widely expected to remain in place.