The government does not think it necessary to refer the National Security Council leak to the police, the PM’s de facto deputy says.
Responding to calls from MPs for a police inquiry, David Lidington said the PM considered the matter closed.
He said Gavin Williamson – who has been sacked as defence secretary – had not been accused of a criminal offence, but had lost the PM’s confidence.
Mr Williamson strenuously denies being the source of the leak.
He was sacked following an inquiry into the leak, which led to reports in the Daily Telegraph on plans to allow Chinese company Huawei to help build the UK’s 5G network.
Opposition MPs have said there should be an investigation into whether the Official Secrets Act had been breached.
But Mr Lidington, responding to an urgent question from Labour deputy Tom Watson, said it was not considered necessary to refer it to the police, but ministers would “co-operate fully should the police themselves consider an investigation necessary”.
Mr Lidington said it “boils down to what is set out in the ministerial code” and so the prime minister was “the ultimate judge of the standards of behaviour expected of a minister”.
He said ministers should “shut up” after National Security Council and cabinet meetings, appearing to echo Mr Williamson’s words when he told Russia to “go away and shut up” soon into his job as defence secretary.
What is the Official Secrets Act 1989?
Disclosure of official information relating to security and intelligence by a “Crown servant” – including government ministers – can be illegal.
For it to be an offence the disclosure has to be damaging and done without lawful authority (ie not as part of the person’s official duties).
Being found guilty of this carries a sentence ranging from a fine to two years in prison.
If the police were to launch an investigation, the Attorney General Geoffrey Cox would decide whether there was to be a prosecution.
But Labour’s Mr Watson, who called for a police investigation, said: “In response to receiving the most brutal sacking I can think of, (Mr Williamson) has protested his innocence.
“Therefore this matter cannot be, as the prime minister says, closed.”
Metropolitan Police Commissioner Cressida Dick said the force would “look at any complaint” made regarding the leak, but it had received no referral from the Cabinet Office.
She said there was a “formal process” for dealing with alleged breaches of Official Secrets Act and police needed a referral.
BBC home affairs correspondent Danny Shaw said a formal “gateway” process for investigating alleged government leaks was put in place after a review of the way the Met dealt with a series of Home Office leaks.
Downing Street has made a very serious accusation and is sure enough to carry out this sacking.
For the prime minister’s allies, it will show that she is, despite the political turmoil, still strong enough to move some of her ministers around – to hire and fire.
Mr Williamson is strenuously still denying that the leak was anything to do with him at all.
There is nothing fond, or anything conciliatory, in either the letter from the prime minister to him, or his reply back to her.
An inquiry into the leak began after the Daily Telegraph reported on the council’s confidential discussions – including warnings from several cabinet members about possible risks to national security over a deal with Huawei.
At a meeting with Mr Williamson on Wednesday evening, Theresa May told him she had information that suggested he was responsible for the unauthorised disclosure.
In a letter confirming his dismissal, she said: “No other credible version of events to explain this leak has been identified.”
In response, Mr Williamson – defence secretary since 2017 – wrote he was “confident” that a “thorough and formal inquiry” would have “vindicated” his position.
“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,” he said.
BBC political editor Laura Kuenssberg said sources close to the former defence secretary had told her Mr Williamson talked to Daily Telegraph’s deputy political editor, Steven Swinford, but “that absolutely does not prove” he leaked the story to him.