Former defence secretary Gavin Williamson has called for an investigation into the inquiry over the Huawei leak that led to his dismissal, after police said they would not be taking action because no crime had been committed.

Williamson was sacked on Wednesday and there were calls for a police investigation given the sensitive nature of the information about the Chinese tech firm’s involvement in the UK’s 5G network leaked from a National Security Council meeting.

However, Metropolitan police said on Saturday that the disclosure had not amounted to a criminal offence and did not contain information that would breach the Official Secrets Act.

“I am satisfied that what was disclosed did not contain information that would breach the Official Secrets Act,” said Neil Basu, head of the Met’s specialist operations. “I have considered all the information available to me and I have taken legal advice. I am satisfied that the disclosure did not amount to a criminal offence either under the Official Secrets Act or misconduct in a public office. No crime has been committed and this is not a matter for the police.”

He said that police had not been provided with evidence by the Cabinet Office that a crime has been committed and no crime had been alleged by the “owner of the material”.

“I am clear that the leak did not cause damage to the public interest at a level at which it would be necessary to engage misconduct in a public office,” he said. “It would be inappropriate to carry out a police investigation in these circumstances.”

Williamson, who strenuously denies being behind the leak, had said he would welcome a police inquiry, which he believed would “absolutely exonerate” him.

The former minister claimed to have been the victim of a “kangaroo court” in the wake of his sacking, and on Saturday described the investigation as a “shabby and discredited witch-hunt”.

“With the Metropolitan police not willing to do an criminal investigation it is clear a proper, full and impartial investigation needs to be conducted on this shabby and discredited witch-hunt that has been so badly mishandled by both the prime minister and Mark Sedwill [the cabinet secretary],” he said, in what marks an escalation of tensions with No 10.

However, Theresa May has said there was “compelling evidence” of his involvement and rejected calls to release an internal leak inquiry report to Williamson so he could see the evidence against him. She has not confirmed whether she is convinced Williamson was the source.

She told Sky News on Friday: “This was an inquiry that was properly conducted, it was conducted in the way in which one would expect an inquiry of this sort to be conducted. As a result of that I took the decision that it was necessary for the then secretary of state for defence to leave his post. This is something that is about the National Security Council and trust in the council.”

Leaked reports of a NSC meeting last month suggested that May had cleared Huawei to be involved in “non-core” elements of the 5G network such as antennas. There are suspicions that Huawei is ultimately controlled by the Chinese state, though these have not been confirmed.

The prime minister reportedly overruled five ministers who expressed concern that the company’s involvement could provide a route for Chinese spying and undermine allies’ confidence in the security of UK communications.

In the ensuing inquiry, Williamson’s call records revealed he had spoken to the Daily Telegraph’s deputy political editor, Steven Swinford, for 11 minutes shortly after the NSC meeting. Williamson has said he told Swinford nothing and has called on the journalist to corroborate his claim.

It is understood the information leaked from the meeting was not deemed by Sedwill to be serious enough to warrant a criminal investigation. MPs were told on Thursday that there were no plans to pass information from the internal inquiry to the police.

Williamson has spoken on Instagram of his “tough week”, posting pictures of himself with his dogs and eating at McDonald’s.

“So the plan had been for dinner this evening with the US defence secretary at Lancaster House. Obviously things change and you just can’t beat a McDonald’s,” he wrote on Friday beneath a photo of him with a drink and fries.