Britain's First Secretary of State Damian Green was forced to resign Wednesday after an investigation found that he had made "misleading" and "inaccurate" statements about pornographic images found on a Parliament computer in his office in 2008. 

Green, a key ally to Prime Minister Theresa May, denied using pornography on his office computers but acknowledged that he had not been forthcoming in statements he made about the matter last month. 

"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," Green said in his resignation letter, which was made public Wednesday night. 

In a letter to Green, May said a report by her cabinet secretary had cleared him of watching or downloading pornography.  However, she added that Green had fallen short of the standards expected of him when he denied police had ever told him that they had found the material in a raid on his office. 

"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 wrote. 

Green was a vital political ally who acted as a de facto deputy prime minister and supported May in her difficult Brexit negotiations.  His removal will cost her an important supporter as she tries to balance competing visions of Brexit within her Cabinet. 

Green had claimed earlier he was the victim of a smear campaign.  The pornography was found on his office computer during a police investigation of government leaks. 

The Cabinet investigation did not yield a conclusion about sexual misconduct allegations writer Kate Maltby made against Green. 

Maltby said Green had "fleetingly" touched her knee during a meeting in a pub and later sent a suggestive text after a picture of her wearing a corset appeared in a newspaper. 

The cabinet secretary investigation said it was "not possible to reach a definitive conclusion" on whether Green's behavior with Maltby was appropriate wily, but added that her account was "plausible." 

Green is among a number of British politicians who have stepped down or been forced out in recent weeks as a wave of allegations of sexual harassment has surfaced.  Last month, Michael Fallon stepped down as defense secretary after a female journalist accused him of trying to kiss her after a lunch meeting in 2003. 

The Associated Press contributed to this report.