Downing Street knew of claims made against sacked cabinet minister Damian Green as early as last year, according to an activist who accused him of inappropriate behaviour.
Kate Maltby told the Daily Telegraph and BBC she informed a senior Number 10 aide of her concerns in 2016.
Green, who denies the claims, was asked to resign from his Cabinet Office role by Theresa May on Wednesday, after an inquiry found he had broken the ministerial code over “misleading” statements about pornography found on his Parliamentary computer.
The probe was sparked after Maltby alleged the MP had touched her knee in a pub in 2015, and sent her a “suggestive” text message the following year.
“Eventually I spoke to a very senior and long-serving aide of Theresa May,” she said.
Maltby told inquiry leader Sue Gray that Downing Street was aware of her allegations “to the best of my knowledge” and the investigation ruled her evidence was “plausible”.
“I was aware that he was the deputy prime minister and I was aware that No 10 knew about it,” she said.
A Downing Street spokesperson denied claims Theresa May knew anything about the allegations last year.
“The PM has made it clear that everyone should be able to work in politics without fear or harassment – that is why she has brought forward a new code of conduct for the Conservative Party, and set up a cross-party working group to make recommendations about the Houses of Parliament,” they added.
Maltby said she decided to speak out with the aim of changing the culture in Westminster.
“My actions in this have never been guided by the quest to claim scalps, to force resignations to end people’s careers,” she added.
“We need an end to the era in which the sexual exploitation of younger people is the sort of peccadillo of a politician.
“That is tolerated by those in power and perhaps exploited to enforce party discipline but not to actually do any good.”
Green apologised to Maltby in his resignation letter.