Damian Green has resigned from his government post as First Secretary of State tonight.

The frontbencher made the shock announcement after a lengthy probe into his conduct.

The investigation is said to have found he had misled the public and MPs over pornography found on an office computer.

The Prime Minister’s de facto deputy was told he had no choice but to quit, and confirmed his resignation in a letter to Mrs May.

The Ashford MP has been the subject of a cabinet inquiry into allegations of inappropriate conduct with a female journalist.

That was then widened to examine claims that pornographic material was found on a computer in his office back in 2008, which the MP also denies viewing or downloading.

In a letter to her long-term colleague Theresa May wrote how she had "carefully considered the report’s conclusions in relation to two statements you made on 4 and 11 November which you now accept were inaccurate and misleading.

"This falls short of the Seven Principles of Public Life and is a breach of the Ministerial Code – a conclusion which has been endorsed by Sir Alex Allan, the Independent Adviser on Ministers’ Interests.

"While I can understand the considerable distress caused to you by some of the allegations which have been made in recent weeks, I know that you share my commitment to maintaining the high standards which the public demands of Ministers of the Crown.

“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.”

The Cabinet Office investigation did not rule on allegations made by writer Kate Maltby that Mr Green sexually harassed her.

Mr Green has served as a member of parliament for Ashford since the 1997 election. He was promoted to the First Secretary role in June this year.