Daniel Korski has stood aside from the race to be Tory candidate for mayor of London following an allegation of groping.
The claim was first made against Mr Korski on 26 June, and he strenuously denied the allegation.
In his withdrawal statement, Mr Korski said he was stepping aside “with a heavy heart”.
He said: “I categorically deny the allegation against me. Nothing was ever put to me formally ten years ago. Nor seven years ago when the allegation was alluded to.
“No investigation has ever taken place. I have been clear I would welcome and constructively participate in any investigation.
“However, the pressure on my family because of this false and unproven allegation and the inability to get a hearing for my message of ‘The London Dream’ makes it impossible for my campaign to carry on.”
TV producer Daisy Goodwin wrote in The Times and Daily Mail that Mr Korski groped her following a meeting 10 years ago in Downing Street.
At the time, Mr Korski was working as an adviser to then prime minister David Cameron.
Ms Goodwin said she had only come forward to name Mr Korski this year because he was standing for public office.
She did, however, write about the allegation in 2017 – albeit without naming Mr Korski.
After he was accused by Ms Goodwin, Mr Korski was asked if the allegation had been disclosed to the Conservative Party in his vetting to be a mayoral candidate.
He told TalkTV: “Yeah, during the process, I was asked about if there were any outstanding issues the party may be aware of.
“And I said to the party, seven years ago, there was a story. I was never named in the story.
Daisy Goodwin. Pic:Ken McKay/ITV/Shutterstock
“As far as I know, there was no investigation. But I did mention this to the party.”
Tory members will vote from 4 to 18 July on their preferred choice for the London mayoral election next year, with the winner announced on 19 July.