Gavin Williamson: Met Police will only launch criminal investigation into Huawei leak if Cabinet Office makes complaint

'The cabinet secretary does not consider it necessary to refer it to the police,' the cabinet office minister David Lidington told MPs

A criminal investigation into allegations Gavin Williamson leaked details of intelligence discussions will only be opened if the Metropolitan Police receives a referral from the Cabinet Office, the force's commissioner has said.

The remarks from Cressida Dick follow Theresa May declaring "the matter closed" after brutally dismissing her defence secretary after a internal inquiry into an unprecedented leak from the government's National Security Council.

Labour and Westminster's other political parties have since called for a criminal investigation into the disclosure of information regarding Chinese telecommunications giant Huawei's access to the UK's 5G mobile network.

But speaking on Thursday, the Metropolitan Police commissioner said that while she would reply to letters from politicians calling for an investigation, officers could not progress without seeing the evidence.

“If the Cabinet Office were to send us a referral at any point that related to apparent official secrets or an associated leak, we would assess that, scope it and go through a very formal gateway process for taking on any criminal investigation,” she told journalists.

When asked if Scotland Yard needed government permission to investigate Mr Williamson, Ms Dick said police would “have to be made party to material [held by the government] and at the present time there is no referral and we are not in possession of that material.”

Ms Dick said the Metropolitan Police had the expertise to investigate Official Secrets Act cases and worked with the Crown Prosecution Service (CPS) on the “complex case law” surrounding them.

Asked whether Mr Williamson could have broken the law by sharing concerns about a governmental decision that would later be made public, Ms Dick said such questions would be addressed by CPS lawyers.

Just moments earlier during an urgent question in the Commons on the issue, however, the cabinet office minister David Lidington repeated the prime minister's comments that the matter is now "closed".

He went on: "The cabinet secretary does not consider it necessary to refer it to the police. We would of course cooperate fully should the police themselves consider that an investigation were necessary."

During the Commons session Dominic Grieve, the former attorney general, said a breakdown in collective cabinet responsibility was partly at fault for the leak.

He said: "Unfortunately what appears to have happened is it has a corrosive quality which starts in the willingness to contradict colleagues over policy issues within the cabinet and then creeps incrementally into a willingness to brief externally on discussions on an increasingly secret nature.

In response, Mr Lidington said he agreed that leaks have had a "corrosive effect", adding: "I do think above all when it comes to National Security Council discussions, and I think this applies to Cabinet too, that there is great merit in the very old-fashioned precept that members should speak with complete candour within the room and shut up when they get outside."

A briefing paper issued in 2017 by the House of Commons library said prosecutions under the Official Secrets Act have been “very rare” – fewer than one a year.

“For members or former members of the security and intelligence services, any unlawful disclosure relating to security or intelligence is an offence,” the report said.

“For Crown Servants [including ministers, civil servants and police] and government contractors, however, an unlawful disclosure related to one of the six categories must be deemed ‘damaging’ for it to constitute an offence.”

The law sets out “damage tests” that require the government to prove that UK’s national interests have been harmed for a case to proceed.

The maximum penalty for an unauthorised disclosure under the Act is two years' imprisonment or an unlimited fine, or both.

Anna Bradshaw, a partner at solicitors’ firm Peters and Peters, said the “damage” does not have to materialise for the law to be broken.

“It is potentially applicable to such a broad range of scenarios that the requirement for authorisation [from the director of public prosecutions or attorney general] acts as a safeguard against over-enthusiastic prosecutions,” she told The Independent.

“It’s difficult to imagine something that wouldn’t potentially be in scope of the law because of the wording of all the provisions. It’s deliberately drafted widely.”

High-profile cases include a case that saw a member of police staff jailed for eight months for passing a Sunday Times journalist information on planned al-Qaeda terror attacks in 2007.

Five years before, MI5 agent David Shayler was jailed for six months for selling information and documents on topics including the IRA and Communist Party of Great Britain to the Mail on Sunday.

In 1983, Foreign Office clerk Sarah Tisdall was given a six-month sentence for passing documents to The Guardian which gave the arrival date of missiles to an RAF base.