Former minister Tim Yeo has lost his battle to be re-selected as the Tory candidate in South Suffolk.
Despite backing from Prime Minister David Cameron, Mr Yeo lost out in a secret ballot of 600 members of his constituency party after the association's executive committee voted not to re-adopt him for next year's general election.
In a statement, Mr Yeo said: "It has been a privilege to serve as MP for South Suffolk since 1983. I will continue to work for all my constituents until the general election next year.
"I am immensely grateful to all those Conservative Party members who voted for me to continue as their MP. I now ask them all to campaign for my successor with the same loyalty and dedication they have shown to me.
"I will give my full and unqualified support to whoever is chosen as the candidate here in South Suffolk. I wish him or her every success."
Party sources said there was an 82% turnout in the ballot, but refused to give details of the margin of defeat. The count - carried out at Tory HQ in London - came just days after another senior Tory colleague, Anne McIntosh, lost a similar de-selection fight in her Thirsk and Malton seat in North Yorkshire.
The South Suffolk executive declined to re-adopt Mr Yeo in December just a month after the Commons sleaze watchdog cleared him of breaking parliamentary rules on lobbying.
The MP had temporarily stood aside as chairman of the influential Energy and Climate Change Committee while the investigation was carried out in the wake of a newspaper "sting".
Reports have suggested his de-selection reflected frustration among some members that he was not devoting enough time to the constituency rather than concerns over the standards inquiry.
In a letter to Mr Yeo last month, Mr Cameron said it would be a "great loss" if he was not re-selected.
"You have served your constituency of South Suffolk for over three decades - a record of which you can be enormously proud," the premier wrote.
"I very much hope that you will be selected to stand as the Conservative representative in this seat again, so that you can fight to continue representing your constituents in the next parliament as you always have done in the past, with tenacity and commitment.
"Your considerable expertise in rural issues and the environment has been of real benefit to our party and our country.
"You have always provided a strong voice for the people of South Suffolk and it would be a great loss to your constituents, to parliament, and to the Conservative Party if the South Suffolk Conservative Association did not re-select you so that you can continue providing that steadfast representation."
Mr Yeo said his support for gay marriage, climate change work and pro-EU stance might have been responsible for his downfall.
He told BBC Radio 4's PM programme: "Clearly there were some issues on which I have may have had disagreements with them.
"I voted in favour of gay marriage, that wasn't a universally held view among my members; I have a very great commitment to addressing climate change, that's not a universally held view; I'm in favour of Britain's membership of the EU, that's not a universally held view either."
He denied suggestions that he had been too low profile, telling the programme his work was backed by the PM, Chancellor George Osborne and Education Secretary Michael Gove.
"I had a lot of people who recognised that, far from being invisible in Parliament, I have actually been one of the most influential chairs of a select committee during this Parliament," he said.
"It was a knife-edge vote," he added.