Sir Keir Starmer will vow to “inject resource and reform” into mental health services as he welcomes MP and psychiatrist Dr Dan Poulter – who quit the Tory Party in anger over the NHS crisis – to Labour.

The Labour leader will promise to “overhaul” the way mental health is approached if he wins the election, on a visit on Monday with his party’s newest MP.

Dr Poulter, a former Tory health minister and part-time working medic, made the shock announcement that he was crossing the floor to Labour on Saturday.

He said Rishi Sunak’s Government was “failing” the NHS and that he could no longer “look my NHS colleagues in the eye” as a Conservative.

“The health service has ceased to be an area of priority for the Conservative Party, and that is now showing in the strain on the front line and the deterioration of care for patients,” he said.

Dr Poulter said “the only cure is a Labour government”, and that he would support Sir Keir and shadow health secretary Wes Streeting on NHS policy.

Sir Keir said “it’s fantastic” that Dr Poulter has joined Labour and will help get the NHS back on its feet.

It comes as Labour pointed to NHS data showing some 120,000 children waited six months or longer between referral for mental health support and treatment in 2022-23, with Sir Keir calling these waits “a scar on a civilised society”.

Appearing alongside Dr Poulter, he will highlight a future Labour government’s focus on mental health reform.

The party plans to improve the Mental Health Act and provide 8,500 specially-trained mental health staff, support in every school and an open access early intervention hub in every community, paid for by closing tax loopholes.

Sir Keir said: “I will not sit on my hands while tens of thousands of people have their lives on hold and ambition curtailed while they languish on mental health waiting lists.

“My Labour government will inject resource and reform into NHS mental health services to not just turn around the shocking figures and give people their lives back, but to completely overhaul the way our country approaches mental health.

“We are mission focused on rebuilding public services and it’s fantastic that Dr Dan Poulter MP has joined us.

“It’s time to end the chaos, turn the page, and get Britain’s future back.”

Dr Poulter will take the Labour whip until the general election but will not be standing again to be the MP for Central Suffolk and North Ipswich, a traditionally safe Tory seat where he was first elected in 2010.

It is the first time a Conservative MP has crossed the floor to Labour since Christian Wakeford did so in 2022.

Dr Poulter’s move is the second defection under Mr Sunak, after former Tory deputy chairman Lee Anderson left the party for Reform earlier this year.

Dr Poulter’s move has heaped pressure on Mr Sunak ahead of what is already expected to be a tough week for the Prime Minister.

It could spook already restive Tory MPs who are considering moving against Mr Sunak in the case of a disastrous set of local and mayoral elections results for the Conservatives on May 2.

Health minister Maria Caulfield said: “Sir Keir Starmer’s own shadow mental health minister resigned over Labour’s failing to take mental health seriously.

“What’s more, where Labour are in power in Wales, they are failing patients with more people left waiting longer for the care they need. Labour would take us back to square one.

“Under the Conservatives, the NHS is receiving record funding, including £4.7 billion more in mental health funding since 2019, and we are driving forward the first ever long-term workforce plan so that we can train the doctors and nurses we need for the future.”