(CNN) British Prime Minister Theresa May has fired her closest political ally after he admitted lying over the presence of pornography on a computer in his parliamentary office.

An investigation by the UK Cabinet Office found that Damian Green's previous denials over the issue were "inaccurate and misleading."

More recently, Green was accused by by journalist and former Conservative party activist Kate Maltby of making unwanted advances towards her during a meeting in 2015.

The loss of Green is a personal blow for May. He was her closest ally in Cabinet, and brokered the deal with the Democratic Unionist Party that kept her in power after her Conservative party lost its parliamentary majority in a botched election in June.

Green is the third cabinet member to leave in the past two months, following the resignations of Defense Secretary Michael Fallon over allegations of inappropriate behavior with women, and of International Development Secretary Priti Patel over unauthorized meetings with senior Israeli politicians.

The Cabinet Office report found that by lying about the pornography, Green had breached the code of conduct for UK ministers. It also said that Maltby's account was plausible, although it was "not possible to reach a definitive conclusion on the appropriateness of Mr Green's behavior" with her.

Green said at the time the allegations were "completely untrue."

May forced Green, the First Secretary of State and her de facto deputy, to resign after the report was published on Wednesday evening.

May said Green's behavior fell short of the standards expected from people in British public life and was a "breach of the ministerial code."

"It is therefore with deep regret, and enduring gratitude for the contribution you have made over many years, that I asked you to resign from the Government and have accepted your resignation," May said in a letter to Green and released by Downing Street.

In his response to May, Green said he did not download or view pornography on his parliamentary computers, calling the allegations "unfounded and deeply hurtful," but went on to admit that he hadn't been clear when he had previously addressed the claims.

"I accept that I should have been clear in my press statements that police lawyers talked to my lawyers in 2008 about the pornography on the computers, and that the police raised it with me in a subsequent phone call in 2013", he said.

"I apologize that my statements were misleading on this point."

In November, May said there needed to be a "new culture of respect" following a wave of sexual harassment scandals at the UK government offices at Westminster, London.