LONDON (Reuters) - British Prime Minister Theresa May forced her most senior minister, Damian Green, to resign for lying about whether he knew pornography had been found on computers in his parliamentary office.

The resignation of one of May’s closest political allies, who had helped pacify her deeply divided party, is a blow as she navigates the final year of tortuous negotiations ahead of Britain’s exit from the European Union in March 2019.

Green, who voted to stay in the EU, was appointed as first secretary of state just six months ago in a bid to shore up May’s premiership following her disastrous bet on a June snap election that lost her party its majority in parliament.

But Green’s future was thrust into doubt when the Sunday Times newspaper reported last month that police in 2008 had found pornography on his office computers in the Houses of Parliament. In response, Green said the story was untrue.

A review, requested by May and conducted by a senior government official, concluded that Green’s statements which suggested he was not aware that indecent material had been found on the computers, were “inaccurate and misleading.”

The inquiry, a summary of which was distributed by May’s Downing Street office, found he had breached rules governing the behavior of ministers because the police had told him about the indecent material.

“I apologize that my statements were misleading on this point,” Green said in a letter to May. “I regret that I’ve been asked to resign from the government.”

Green, 61, said he did not download or view pornography on his parliamentary computers. He added that he should have been clearer about his statements after the story broke.

May said she had asked him to resign and accepted his resignation with deep regret.

He is the most senior British politician to fall since the Harvey Weinstein sexual harassment scandal triggered a debate about a culture of abuse by some powerful men at the heart of Westminster.

May’s defense minister, Michael Fallon, quit last month for unspecified conduct which he said had fallen below required standards. Her aid minister resigned a week later after holding undisclosed meetings with Israeli officials.

CONDUIT FOR COMPLAINTS

During the turmoil that followed the botched election, May turned to Green -- a university friend from their days at Oxford -- to stabilize her premiership and appease those within the Conservative Party who wanted her to quit.

One of his key roles was to act as a conduit for disgruntled party members who felt they had been ignored in May’s election campaign. He sought to help her to shed the image of a distant leader who only listens to those in her inner circle.

“It’s another blow for May but it is not deadly in any way at all,” said Anand Menon, professor of European politics at King’s College London. “She has lost her soulmate in cabinet but this is not the end of Prime Minister May.”

“May is surviving not because of Damian Green but because there are sufficient MPs in her party who don’t want to have a leadership election while Brexit is going on and that fundamental calculation has not changed,” he said.

The internal investigation found that Green’s conduct as a minister was generally “professional and proper” but found two statements he made on Nov. 4 and 11 to be inaccurate and misleading.

FILE PHOTO: Damian Green, Britain's Prime Minister Theresa May's deputy, leaves his home in London, November 6, 2017. REUTERS/Peter Nicholls

In the statements, Green suggested he was not aware that indecent material had been found on his computers.

The inquiry said Green’s statements had fallen short of the honesty requirements for those in public life and thus constituted breaches of the ministerial code of conduct.

The allegations about pornography were publicly aired by former Metropolitan Police assistant commissioner Bob Quick, drawing a rebuke from the head of the London police, Cressida Dick, who said officers had a duty of confidentiality.

May, who served as home secretary for six years before winning the top job, said she shared concerns about the comments made by the former police officer.

WESTMINSTER SCANDAL

Sexual abuse allegations against Hollywood producer Weinstein have prompted some women and men to share stories about improper behavior at the heart of British political power in Westminster.

The internal investigation also addressed allegations, made by the daughter of a family friend, that Green had made an unwanted advance towards her during a social meeting in 2015, had suggested that this might further her career, and later had sent her an inappropriate text message.

The report said it was not possible to reach a definitive conclusion on the appropriateness of Green’s behavior in that instance, though the investigation found allegations to be plausible.

Green said in his resignation letter that he did not recognize the account of events, but apologized to the woman, academic and critic Kate Maltby, for making her feel uncomfortable.