The leak from the meeting of the National Security Council about Huawei “did not amount to a criminal offence”, the Metropolitan Police has said.
Defence Secretary Gavin Williamson was sacked after an inquiry into the leaking of details from the council.
Opposition MPs had said there should be an investigation into whether the Official Secrets Act had been breached.
But Metropolitan Police Assistant Commissioner Neil Basu said he was “satisfied” it had not.
The leak from the council’s confidential discussions led to reports in the Daily Telegraph about a plan to allow Huawei limited access to help build the UK’s new 5G network.
The newspaper also reported on subsequent warnings from within cabinet about possible risks to national security over any deal with the Chinese firm.
Mr Williamson strenuously denied being responsible for the leak, but Prime Minister Theresa May said she had lost confidence in his ability to serve.
At a meeting with Mr Williamson on Wednesday evening, Mrs 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.”
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.
Mr Basu, who is Britain’s top counter-terrorism police officer, said that what was disclosed “did not contain information that would breach the Official Secrets Act”.
He added: “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.
“It would be inappropriate to carry out a police investigation in these circumstances.”
Mr Basu said the decision was informed by conversations with the Cabinet Office about the nature of the matters discussed at the meeting. He also took legal advice.
Mr Williamson – who had been defence secretary since 2017 – responded to his sacking by saying he was “confident” that a “thorough and formal inquiry” would have “vindicated” his position.