MP Patrick Mercer has resigned the Tory whip as the BBC plan to screen a programme that alleges he broke lobbying rules.
The Newark MP, whose constituency covers the Southwell area, said he will not be standing at the next general election but there will not be a by-election.
Mr Mercer, who has referred himself to the parliamentary standards commissioner, said he was “taking legal advice” about the allegations but said he wanted “save my party embarrassment” by stepping down from his role.
Mr Mercer said in a statement: “Panorama are planning to broadcast a programme alleging that I have broken Parliamentary rules.
“I am taking legal advice about these allegations - and I have referred myself to the Parliamentary Commissioner for Standards.
“In the meantime, to save my Party embarrassment, I have resigned the Conservative Whip and have so informed Sir George Young.
“I have also decided not to stand at the next general election.”
MPs who resign the whip can continue to sit in the Commons as independents but are no longer members of the parliamentary party.
Mr Mercer (57) said he intends to continue as the MP for Newark but as an independent rather than a Tory.