Great Yarmouth MP Brandon Lewis has resigned from prime minister Rishi Sunak's government.
Mr Lewis had served in Liz Truss' cabinet as lord chancellor and secretary of state for justice.
He had served on the front bench of successive governments for 10 years and had been in the cabinet for five years.
In that time he had held eight ministerial posts across five departments.
His resignation letter to Mr Sunak said: "Congratulations on your election as Leader of our Party and Prime Minister of our great country.
"Having taken the time to consider my position, I am writing to submit my resignation from the Government."
His letter added: "Our Party is at a crossroads. We now have an opportunity to reunite and rebuild and we must take it.
"We must come together and deliver the mandate we were given by the British people.
"We have a duty to the country to do so, at a time of economic hardship for so many.
"It is no exaggeration to say that the future of the Conservative Party and everything we stand for is at stake if we do not.
"You will have my support from the back benches in addressing the economic crisis we face, bringing our Party together and delivering on the promises we put forward in the 2019 manifesto, on which we won such an overwhelming majority."
Mr Lewis's resignation letter mentions his role as secretary of state for Northern Ireland and how he guaranteed the largest funding settlement for Northern Ireland since devolution in 1998.
it also mentions he was pleased to have helped introduce the Northern Ireland Troubles (Legacy and Reconciliation) Bill to parliament.
The letter also says that as secretary of state for justice, Mr Lewis had radically expanded tagging and supervision of burglars, thieves and robbers and had taken a big step forward in reducing the court system backlog and ensuring justice for victims of crime.
His letter also said: "It has been the honour of my life to serve on the front bench over the last ten years and in Cabinet for the last five of those under four Prime Ministers.
"In that time I have been privileged to hold eight ministerial jobs across five departments."
In the leadership race after Boris Johnson's resignation, Mr Lewis had backed Nadim Zahawi and then switched to Ms Truss.
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