Bury South MP Christian Wakeford has defected to the Labour Party.
Mr Wakeford was elected to the seat as a Conservative at the 2019 election, but has been a vocal critic of Prime Minister Boris Johnson in recent weeks.
He was among a number of MPs to call for the PM to quit after a series of Downing Street parties during lockdown and branded the scandal as 'embarrassing' in a series of damning comments last week.
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In an open letter to Boris Johnson, Mr Wakeford described the Prime Minister's conduct as 'disgraceful'.
He added: "I am in no doubt that [Bury South] will be better served by my joining a party that genuinely has their interests at heart."
The Labour Party announced his dramatic switch on Twitter on Wednesday morning (January 19).
The tweet read: "A very warm welcome to Christian Wakeford MP! The new Labour MP for Bury South."
Labour’s leader Sir Keir Starmer said he welcomed Mr Wakeford's move, which was announced just minutes before Prime Minister's Questions.
"He has always put the people of Bury South first," he said in a statement.
Sir Keir said the "Conservative government are doing nothing to help the people of Bury South and indeed are only making the struggles they face on a daily basis worse".
“People across Britain faces a cost of living crisis but this incompetent Tory government is asleep at the wheel, distracted by a chaos of its own making," Sir Keir says.
In a pointed message to Boris Johnson last week, Mr Wakeford called for "openness, trust and honesty" in politics, and "that starts from the top."
He said on Twitter: "How do you defend the indefensible? You can’t!
"It’s embarrassing and what’s worse is it further erodes trust in politics when it’s already low.
"We need openness, trust and honesty in our politics now more than ever and that starts from the top!"
The government is yet to comment on Wakeford's defection.
Christian Wakeford's letter in full
Dear Prime Minister,
I am writing to inform you of my decision to resign from the Conservative Party and apply to join the Labour Party.
From today I will be sitting as the Labour MP for Bury South because I have reached the conclusion that the best interests of my constituents are served by the programme put forward by Keir Starmer and his party.
I care passionately about the people of Bury South and I have concluded that the policies of the Conservative government that you lead are doing nothing to help the people of my constituency and indeed are only making the struggles they face on a daily basis worse.
Britain needs a government focused on tackling the cost of living crisis and providing a path out of the pandemic that protects living standards and defends the security of all. It needs a government that upholds the highest standards of integrity and probity in public life and sadly both you and the Conservative Party as a whole have shown themselves incapable of offering the leadership and government this country deserves.
Being elected as MP for Bury South was the proudest day of my life. I care passionately about the area and will always be grateful to those who have supported me. Today, however, I am in no doubt that they will be better served by my joining a party that genuinely has their interests at heart.
I have wrestled with my conscience for many months, and you will know that I have made my policy misgivings clear on many occasions in private and sometimes in public. I can no longer support a government that has shown itself consistently out of touch with the hard working people of Bury South and the country as a whole.
Under Keir Starmer, the Labour Party is back firmly in the centre of British politics, in touch with working people, and ready to provide an alternative government that this country can be proud of, and not embarrassed by.
My decision is about much more than your leadership and the disgraceful way you have conducted yourself in recent weeks. However, I don’t believe all politicians are the same and I do believe in the power of politics to be a force for good. So does Keir Starmer. He has shown that integrity in the way he has led his party on issues that matter to me, not least the vital challenge of combatting antisemitism.