A formal inquiry has begun into the leaking of discussions about Huawei at the National Security Council, the BBC has learned.
This follows the Daily Telegraph publishing details of a meeting about using the Chinese telecoms firm to help build the UK’s 5G network.
Several cabinet ministers have denied they were involved in the leak.
Cabinet Secretary Sir Mark Sedwill is leading the inquiry, BBC political editor Laura Kuenssberg said.
The National Security Council (NSC) is made up of senior cabinet ministers and its weekly meetings are chaired by the prime minister, with other ministers, officials and senior figures from the armed forces and intelligence agencies invited when needed.
It is a forum where secret intelligence can be shared by GCHQ, MI6 and MI5 with ministers, all of whom have signed the Official Secrets Act.
But following Tuesday’s meeting, the Daily Telegraph reported that the NSC had agreed to allow Huawei limited access to help build Britain’s new 5G network, amid warnings about possible risks to national security.
It also reported that various ministers had raised concerns about the plan.
Culture Secretary Jeremy Wright told MPs: “We cannot exclude the possibility of a criminal investigation here and everyone will want to take seriously that suggestion.”
Amid speculation about who was behind the leak, several ministers have denied any involvement.
Home Secretary Sajid Javid said divulging sensitive information was “completely unacceptable”, adding: “If it happens it should absolutely be looked at.”
Defence Secretary Gavin Williamson and Foreign Secretary Jeremy Hunt denied the leak had come from them, with Mr Hunt calling it “utterly appalling”.
Sources close to International Trade Secretary Liam Fox also categorically denied that he had been involved.
According to the Daily Telegraph, Huawei would be allowed to help build the “non-core” parts of the UK’s 5G network, such as antennas.
There has been no formal confirmation of Huawei’s role in the 5G network and No 10 said a final decision would be made at the end of spring.
Huawei has denied there is any risk of spying or sabotage, or that it is controlled by the Chinese government.
Earlier, former Defence Secretary Sir Michael Fallon told the BBC: “All those involved should be investigated now to find out who this leaker is.
“Ministers are subject to the Official Secrets Act just like anybody else. It is an offence to divulge secret information from the most secret of all government bodies, which is the National Security Council. It has got to be stopped.”
When questioned, Prime Minister Theresa May replied: “We don’t comment on leaks and on those matters.
“On the overall matter of security and our telecoms network, we are very clear that we give that high priority. We want to ensure we see greater resilience in our telecoms network and that we are able to provide high levels of cyber security, but we also see diversity of suppliers.”