The chairman of one of the UK's biggest NHS trusts was asked to consider resigning on Friday, two days before he quit in protest, Sky News can reveal.
Lord Kerslake announced he was stepping down as chairman of King's College Hospital NHS Foundation Trust in London in a statement on Sunday.
He said he was resigning in protest over what he claimed was the Government's "unrealistic" approach to the huge challenges around funding.
It is understood the new chair of regulator NHS Improvement, Dido Harding, spoke to Lord Kerslake on Friday and asked him to "consider his position" in the light of consistently poor financial performance at the trust, which has the largest deficit in the health service.
Yet, in a statement Lord Kerlake released on Sunday night, he said: "I do not do this lightly as I love King's but believe the Government and regulator are unrealistic about the scale of the challenge facing the NHS and the trust.
"I want to pay tribute to the staff and their excellent patient care."
In a self-penned article in The Guardian, he went on to pay tribute to the "world-class" care given at the hospital, especially after the Westminster and London Bridge terror attacks.
"King's, like many other hospitals, is fighting against the inexorable pressures of rising demand, increasing costs of drugs and other medical supplies, and the tightest spending figures in recent times," he wrote.
"There are undoubtedly things that I and the trust could have done better, there always are, but fundamentally our problems lie in the way that the NHS is funded and organised.
"We desperately need a fundamental rethink. Until then we are simply 'kicking the can down the road'."
The hospital described Lord Kerslake as a "passionate advocate and champion" of the trust.
"With a heartfelt commitment to staff and patients, he has led King's through a challenging period which has also seen some notable successes, our response to three major incidents in London, the launch of the helipad and delivering some of the highest patient outcomes of any trust in the UK," a statement added.
But NHS Improvement branded the hospital's financial performance "unacceptable", adding: "It is the worst in the NHS and continues to deteriorate."
Lord Kerslake is a member of the House of Lords, president of the Local Government Association and former head of the civil service and permanent secretary at the Department for Communities and Local Government.
Labour's shadow health secretary, Jonathan Ashworth, said Lord Kerslake's decision was "embarrassing for the Government" and that "seven years of underfunding is impacting on patients in unacceptable ways".
A Department of Health spokeswoman said: "We know that King's NHS Foundation Trust faces huge financial challenges and we will support them to tackle these issues and continue to deliver high quality care for patients under a new chairman.
"We would like to thank Lord Kerslake for his service."
A spokesperson for NHS Improvement added: "We are considering a range of actions (for King's), including entry to our Financial Special Measures regime, which means King's will be subject to greater scrutiny and extra support from NHS Improvement.
"We respect Sir Bob Kerslake's decision to step down and will replace him with a highly experienced new chair to take charge of the trust's position."