Gavin Williamson has been sacked as Defence Secretary over the unprecedented leak of information from a National Security Council meeting, Downing Street has announced.

A probe was launched after highly confidential and sensitive details about Theresa May’s plan to allow Chinese telecoms firm Huawei to build part of the UK’s 5G network were handed over to The Telegraph.

It is the first time a minister has been sacked for leaking secrets in modern times.

Mr Williamson denied being the leaker today, writing in a letter to the prime minister that neither he nor his team were responsible.

“I strenuously deny that I was in any way involved in this leak and I am confident that a thorough and formal inquiry would have vindicated my position,” he wrote.

Opposition MPs have called for a criminal investigation. Deputy Labour leader Tom Watson said: “If he has leaked from the National Security Council, Gavin Williamson should be prosecuted under the Official Secrets Act.”

After the meeting the Telegraph reported Mr Williamson was one of a small group of ministers who objected to Mrs May’s decision but were overruled.

Critics of the deal with Huawei argue it risks allowing China to spy on and interfere with UK communications.

In a meeting with Mr Williamson on Wednesday evening, Mrs May confronted him with information which she said provided “compelling evidence” that he was responsible.

In a letter confirming his dismissal, she wrote: “No other, credible version of events to explain this leak has been identified.”

Mrs May said that the leak from the April 23 meeting was “an extremely serious matter and a deeply disappointing one”.

Women and Equalities minister Penny Mordaunt has been appointed Defence Secretary, becoming the first woman to ever hold the post.

A Downing Street spokesman said today: “The Prime Minister has this evening asked Gavin Williamson to leave the Government, having lost confidence in his ability to serve in the role of Defence Secretary and as a member of her Cabinet.

“The Prime Minister’s decision has been informed by his conduct surrounding an investigation into the circumstances of the unauthorised disclosure of information from a meeting of the National Security Council.

“The Prime Minister thanks all members of the National Security Council for their full cooperation and candour during the investigation and considers the matter closed.”

Top civil servant Sir Mark Sedwill launched the investigation and demanded ministers co-operate with his inquiry.

Culture Secretary Jeremy Wright warned the government cannot rule out the possibility of a criminal investigation after the secrets were handed to the press.

While leaks from ministerial meetings are not uncommon, it is unprecedented for secrets from a forum where the most senior people in Government are briefed by heads of the security and intelligence agencies to reach the public.