Care Quality Commission chair Jo Williams has announced she is to step down from the regulator.
The announcement comes just days before Dame Jo is due to appear at health select committee where she was likely to face a grilling from MPs and questions about her position.
In a message to staff Dame Jo said she would be staying on until her successor was appointed, meaning she will still appear at the accountability hearing.
Dame Jo has faced calls for her resignation since she tried and failed to have a board colleague sacked last year.
She contacted former health secretary Andrew Lansley asking him to dismiss non-executive director Kay Sheldon on the day she gave evidence to the Mid Staffordshire Foundation Trust Public Inquiry, where chairman Robert Francis described her as a whistleblower.
Mr Lansley declined her request.
In a statement Dame Jo said: “Having served on the board of the CQC for almost four years, and as chair for nearly three, I am proud of the progress we have made.
“It has been a demanding and complex role, and there have undoubtedly been challenges as we registered 40,000 providers and brought the entire health and social care system under one set of standards.
“But there is now clear evidence that our regulation is beginning to have an impact on the care that people receive, and it feels as if the organisation is moving into the next stage of its development.
“This week, we have published a consultation document setting out proposals for CQC’s strategic direction for the next three years.
“And I am delighted that that I have been able to appoint David Behan as CQC’s new chief executive - I am confident that he will continue to build on the progress that we have made in promoting and protecting the health and safety of people who use services.
“‘It has been a privilege to hold this important role but I now believe it is time to step aside and for a new chair to lead CQC into the next stage.”
Una O’Brien, permanent secretary at the department of health, said: “I would like to thank Jo for her tireless and dedicated service in leading the CQC as chair since 2010, and before that as a Non-Executive Director from its inception in 2008.
“Jo has shown sustained loyalty and commitment to the organisation, and to the patients and the public its serves. She is leaving the CQC well prepared for the next phase of its development.”
Sir Christopher Kelly, former permanent secretary of the Department of Health, and Andrew Dilnot, chair of the Commission on Funding of Care and Support, also paid tribute to her leadership.
Mr Dilnot said: “I have enormous admiration and respect for Dame Jo; her insight, experience and commitment were invaluable to the work of the Commission of Funding of Care and Support, which reported last summer.
‘While she will be much missed in her position as CQC chair, I hope that adult social care will continue to benefit from her contribution via other forums.”