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. Ministers would, however, “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.

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.”

Mr Lidington said Mr Williamson had “not been accused of any criminal offence” but had “lost the confidence of the prime minister”, who by sacking him “acted within the ministerial code”. But Conservative MP Sir Desmond Swayne argued the process had not been fair, saying: “Natural justice requires that the evidence is produced so that [Mr Williamson’s] reputation can be salvaged or utterly destroyed, doesn’t it?”

Before Mr Lidington made his statement to the Commons, his parliamentary private secretary was photographed holding a document – seemingly intended to be hidden from view – stating that the prime minister’s decision “does not affect” Mr Williamson’s membership of the Privy Council.

The body, whose members are referred to as “right honourable”, is made up of about 600 people, including past and present cabinet ministers.

Meanwhile, 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.

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.