A Conservative MP and former minister has crossed the floor and joined Labour.
Dr Dan Poulter said he could "no longer look people in the eye" and has called for an immediate general election.
The MP for Central Suffolk and North Ipswich, who works part time as a doctor, said that Conservatives were no longer focused on public services.
Dr Poulter has been a Member of Parliament since 2010.
Dr Dan Poulter has crossed the floorUK Parliament/WikiCommonsWriting in The Observer, he said: "I have to be able to look my NHS colleagues in the eye, my patients in the eye and my constituents in the eye.
"And I know that the Conservative government has been failing on the thing I care about most, which is the NHS and its patients."
Dr Poulter has become the second ex-Tory to join Labour since the 2019 election, following Christian Wakeford crossing the floor in 2022. Dr Poulter said he would not seek re-election to the House of Commons at the next general election.
Labour Leader Sir Keir Starmer said: "It’s fantastic to welcome Dr Dan Poulter MP to today’s changed Labour Party. It’s time to end the Conservative chaos, turn the page, and get Britain’s future back. I’m really pleased that Dan has decided to join us on this journey."
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Dr Dan Poulter MP in 2013
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Dr Poulter suggested the Tories had stopped valuing public services.
He said: "The difficulty for the Conservative Party is that the party I was elected into valued public services... it had a compassionate view about supporting the more disadvantaged in society. I think the Conservative Party today is in a very different place."
Shadow Health Secretary Wes Streeting said: "Proud to welcome Dr Dan Poulter MP to the @UKLabour Party. As a frontline clinician, he’s seen the damage that 14 years of Conservative government have done to our NHS.
"Delighted to have his support and look forward to working with him, especially on mental health reform."
In his letter to Prime Minister Rishi Sunak, Dr Poulter said: "It is this that has led me to resign from the Conservative Party to focus on my work as a doctor and, at the same time, I will be supporting the Labour Party to deliver a better NHS.
"Regrettably, I have come to the conclusion that only the Labour Party has the trust and the will to restore a failing health service which is currently unable to deliver the care patients need and deserve."