JEREMY Hunt has undermined Theresa May’s bid to draw a line under the Gavin Williamson leak row by insisting that the police and not politicians must decide if there should be a criminal investigation.

The Foreign Secretary’s intervention piles the political pressure on the Prime Minister to call in Scotland Yard in relation to her sacking of the former Defence Secretary over the unprecedented security leak from the National Security Council.

Downing St has repeatedly made clear Mrs May now regards the matter as “closed” and the Metropolitan Police has confirmed that only the Government can refer the matter for investigation.

But speaking during his Africa tour at a world press freedom day forum in Addis Ababa in Ethiopia, Mr Hunt said: “When it comes to issues like whether there should be a police investigation or not, there’s a very, very important principle of our system that those decisions are not made by politicians, they are made independently by police.

“And that has to be the correct way forward in this situation,” he added.

Mr Williamson was sacked by the PM after an inquiry overseen by Sir Mark Sedwill, the National Security Advisor, said there was “compelling evidence” the former Secretary of State was responsible for leaking sensitive information from the NSC to the Daily Telegraph about the Government’s controversial decision to allow the Chinese tech giant Huawei to get involved in building Britain’s 5G network.

The Staffordshire MP denies he was the leaker and claims he has been the victim of a Government “witch-hunt” and, moreover, that if there were a police probe, he would be exonerated.

At Westminster, David Lidington, Mrs May’s de facto deputy, was accused of being “casual with the facts” after he responded to an Urgent Question in the Commons on the Williamson case.

The Cabinet Office Minister insisted the Government would fully co-operate with Scotland Yard should it deem it necessary to launch a criminal investigation.

However, Cressida Dick, the Met Commissioner, made clear that the force could only investigate the matter of whether Mr Williamson had broken the Official Secrets Act if it received a referral from the Cabinet Office, where Mr Lidington is the lead minister.

Raising a Point of Order in the Commons chamber, Stewart McDonald for the SNP suggested Mr Lidington was fully aware that his office would not refer the matter to the police even though he had offered Scotland Yard the Government’s full co-operation with one.

“He must have known when he was on his feet, responding to questions that that was the case,” declared Mr McDonald. “They could not co-operate with a police investigation that the Government has no intention of asking the police to proceed with,” he explained.

Suggesting there was a “degree of being casual with the facts,” the Glasgow MP urged Mr Lidington to return to the House to clarify what the Government’s position was and “what its role might be in getting, what many in this place believe to be pivotal, the police to investigate the entire sorry affair”.

Deputy Speaker Eleanor Laing responded by saying: “If there are matters to be discussed further by the minister in question I have no doubt he will, assiduously as ever, carry out his duties and come to this House and answer those questions.”

During Commons exchanges, Tom Watson, Labour’s deputy leader, told MPs: “The essential point here is that the Prime Minister has sacked the Secretary of State for Defence because she believes there is compelling evidence that he has committed a crime but, despite that, she does not believe that he should face a criminal investigation.

“Where is the justice in that? In what world is it acceptable that the Prime Minister should be the arbiter of whether a politician she believes is guilty of criminal conduct in office should face a criminal investigation?”

Mr Lidington told MPs: "The Prime Minister has said she now considers that this matter has been closed and the Cabinet Secretary does not consider it necessary to refer it to the police.

"But we would of course co-operate fully should the police themselves consider that an investigation were necessary."

The minister refused to say whether he thought Mr Williamson did or did not break the law, saying this was not a matter for him. “Whether a criminal offence has been committed is a matter of independent prosecution authorities and ultimately for the courts,” he said.

In another Point of Order, Mr Watson referred to Ms Dick’s explanation of procedure; that a referral for an investigation had to come from the Cabinet Office. Looking at Mr Lidington, he asked: “Will the Deputy Prime Minister clear this matter up…Perhaps he could agree to share the information with the police from the dispatch box?”

Mr Lidington declined to respond.

Labour together with the SNP and Liberal Democrats have demanded a police probe; Jo Swinson, the Lib Dems’ deputy leader, has written to the Met calling for one.

But Ms Dick explained how her force would always look at any complaint but to launch a formal inquiry it was necessary to have a referral from the Government.

She said any official secrets would be owned by the Government and it would hold any evidence relating to them.

"It is sitting in the Government. We as the police when considering whether there is an appropriate criminal investigation or not will have to be party to that material. At the present time we are not in possession," added the Commissioner.