Nick Boles, the MP for Grantham and Stamford, has announced he is resigning from his local Conservative association after a dispute over his position on Brexit.
Mr Boles, a former Remainer, supports Theresa May’s deal with Brussels but has also been advocating a softer “Norway Plus” form of Brexit involving membership of the European Economic Area.
He has also worked with the senior Labour MP Yvette Cooper on amendments designed to prevent the UK crashing out of the EU without a deal.
Earlier this week, Mr Boles rebelled against the government when he voted for a parliamentary amendment opposing a no-deal Brexit in all circumstances.
In a letter to members first seen by the BBC, Mr Boles said: “I am not willing to do what would be necessary to restore a reasonable working relationship with a group of people whose values and views are so much at odds with my own.”
He told his local party: “I regret that my relationship with you should end in this way. But a politician without principles is worthless. I am in no doubt about my duty, which is to be true to my convictions and to dedicate the rest of my time in parliament to the best interests of the people I was elected to serve.”
Mr Boles said he wanted to continue to “take the Conservative whip”. Julian Smith, UK Chief Whip, said the MP was a “valued member of the Conservative parliamentary party which I hope will continue to benefit from his ideas and drive”.
In February, his association voted unanimously to start the process of selecting the constituency’s candidate for the next election.
In a letter to local members, vice president of the association Councillor Martin Hill said they had been “betrayed by their parliamentary representative” and called on Mr Boles to stand down as an MP.
“As you are all aware, Nick has been at odds with the local party and the prime minister for some time, so this announcement does not come as a complete surprise, but the timing does leave a lot to be desired”, he wrote.
“I understand that it is Mr Boles’s intention to carry on as the MP for Grantham and Stamford until the next general election, despite being elected to represent us in parliament.”
Mr Hill later told the BBC: “Talk to the man and woman on the street and they’re also quite angry that their MP seems to be going back on what he promised to do at the general election.”