Sir Mike, a former oncologist, was appointed to the post in April.

He said: 'We have made progress on several critical improvements. I am particularly pleased that we now have specialist sector teams in place and will shortly be communicating the consultation response on the new Assessment Approach.

'However, it has become increasingly clear that the turnaround of the CQC—alongside the work required to establish it as the world's leading health and care regulator—will demand a longer-term commitment as chair than I am able to make.'

He added: 'I remain fully committed to the CQC's future success and to supporting any incoming chair during the transition.'

Dr Arun Chopra, interim chief executive of the CQC, said: 'On behalf of the leadership team and the wider organisation, I would like to thank Sir Mike for his contribution to rebuilding the CQC - from his Independent Review and in his role as our chair over the last year.

'We are committed to delivering on the recommendations that he made and to rebuilding our organisation so that we deliver for patients and people who use services.'