Photo: PA

Gavin Williamson has been sacked as defence secretary after a leak investigation led by cabinet secretary Sir Mark Sedwill concluded there was “compelling evidence” he was responsible for unauthorised disclosure of information from the National Security Committee.

Prime minister Theresa May said yesterday said she could "no longer have full confidence" in Williamson following the probe. The investigation was launched after it was revealed that ministers had decided Huawei could provide some elements of the equipment for the UK's future 5G data network, despite warnings of a security risk. It is believed the decision was taken at a meeting of the government's National Security Council, and subsequently briefed to The Daily Telegraph.

Sedwill launched an inquiry [1] after details of the discussions appeared in the press, and May told Williamson yesterday that the investigation provided "compelling evidence suggesting your responsibility for the unauthorised disclosure”.

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In a letter announcing his sacking, May said the leak was "an extremely serious matter, and a deeply disappointing one".

She added: "That is why I commissioned the cabinet secretary to establish an investigation into the unprecedented leak from the NSC meeting last week, and why I expected everyone connected to it – ministers and officials alike – to comply with it fully. You undertook to do so.

"I am therefore concerned by the manner in which you have engaged with this investigation. They have all answered questions, engaged properly, provided as much information as possible to assist with the investigation, and encouraged their staff to do the same. Your conduct has not been of the same standard as others.

"In our meeting this evening, I put to you the latest information from the investigation, which provides compelling evidence suggesting your responsibility for the unauthorised disclosure. No other, credible version of events to explain this leak has been identified."

Williamson has been replaced by international development secretary Penny Mordaunt, the first woman to hold the post. Her role at the Department for International Development has been taken by prisons minister Rory Stewart.

However, Williamson has denied he had anything to do with the unauthorised briefing and said yesterday that his sacking was the result of “a vendetta between him and Mark Sedwill”.

Spoken to Gavin Williamson. He swore on his children’s life to me that he didn’t leak the Huawei news and neither did his staff. Said he believes this is the settling of a vendetta between him and Mark Sedwill

— Alistair Bunkall (@AliBunkallSKY) May 1, 2019 [5]

In a letter to the prime minister, he said he "strenuously" denied being responsible for the briefing.

He added: “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.

“I have always trusted my civil servants, military advisers and staff. I believe the reassurances they have given me.

“I appreciate you offering me the option to resign, but to resign would have been to accept that I, my civil servants, my military advisers or my staff were responsible; this was not the case.

“Restoring public confidence in the NSC is an ambition we both share. With that in mind I hope that your decision achieves this aim rather than being seen as a temporary distraction.”

FDA general secretary Dave Penman told CSW that Williamson's claim of a vendetta “beggars belief”.

He said: “What is too quickly forgotten here is that this is not simply another episode on the ongoing political psycho drama surrounding the current government, but a matter of national security.

“Ultimately, this was a decision for the prime minister based on the evidence available. As Theresa May’s devastating letter to Gavin Williamson lays out, not only did he fail to fully cooperate with the investigation, but she concluded that he was the source of the leaks.

“Within the last week, Williamson sought to blame officials for the leak itself and then accused the Cabinet Secretary of waging a personal vendetta against him. His suggestion that May would dismiss her defence secretary – a political ally – based on Mark Sedwill’s personal agenda beggars belief.

“Unfortunately, as we have seen all too often recently, it is easier to throw unsubstantiated allegations at the civil servant advising the prime minister, than address the substance of her decision.”