Prime Minister Theresa May has fired her defense minister over a leak of discussions in the National Security Council about Chinese telecoms company, Huawei.

Gavin Williamson on Wednesday became the latest of May’s allies to be ousted from government.

Williamson who doggedly denied involvement in the leak, was another blow for May, whose own premiership hangs by a thread after her failure so far to usher Britain smoothly out of the European Union.

The firing also underlined how seriously her team treated the leak from the National Security Council, which discusses Britain’s national security, intelligence coordination and defense strategy, and involves only certain ministers from her cabinet to keep its talks as secret as possible.

The secrecy was revealed last month when Telegraph newspaper reported Britain would allow Huawei a role in building parts of its 5G network, setting London at odds with Washington over the next generation of communications technology.

Sources were forced to say that the role would be limited.

Mrs May in a letter to Williamson said an investigation into the leaks had provided “compelling evidence suggesting your responsibility for the unauthorized disclosure”.

“No other, credible version of events to explain this leak has been identified,” she added after putting the “latest information from the investigation” to Williamson earlier on Wednesday.

Williamson denied the accusation.

“I am sorry that you feel recent leaks from the National Security Council originated in my department. I emphatically believe this was not the case.

“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.”

Mrs May has appointed international development minister Penny Mordaunt to succeed Williamson as defense secretary, and named prisons minister Rory Stewart to Mordaunt’s former role.

This makes Mordaunt Britain’s first woman defense minister.

May has overseen several departures in her cabinet, with many quitting rather than being pushed.

One notable exception was Boris Johnson, now one of her strongest rivals, who quit last year in protest at her plans to keep close trade ties with the European Union after Britain leaves the bloc, stirring rebellion in her party’s ranks.

The tech company, Huawei, the world’s biggest producer of telecoms equipment, is under intense investigation after the United States told allies not to use its technology because of concerns it could be a vehicle for Chinese spying.

Huawei has denied this.