Cabinet members who were at Tuesday’s National Security Council (NSC) have been sent an ultimatum by Whitehall’s most powerful official to confess or deny whether they leaked a controversial decision to allow Chinese telecoms firm Huawei to help build the UK’s 5G phone network.

Cabinet secretary Sir Mark Sedwill is understood to have written to those present and demanded that they tell him by 2pm on Thursday whether they were involved and would be willing to cooperate with an inquiry, prompting the five prime suspects to scramble to “categorically deny” that they were behind the leak.

The move came at an acutely sensitive time as several of those present are hoping to take over as prime minister when Theresa May steps down. There are also growing calls for whoever did leak the information to the Daily Telegraph to be prosecuted under the Official Secrets Act.

Sedwill also asked the senior ministers present to agree that their special advisers, and any officials who had access to information about the outcome of the NSC meeting, would also assist the inquiry.

The NSC meeting had decided to allow Huawei to supply some “non core” telecoms equipment for next-generation phone networks in the UK and the initial focus over the leak has centred on the five ministers present who were opposed to Huawei’s having any involvement in 5G.

Profile Mark Sedwill: UK's top civil servant Show Hide Sir Mark Sedwill became Britain’s most powerful civil servant in autumn 2018, after it became clear that predecessor Sir Jeremy Heywood was terminally ill. He took the job without having to go through a formal interview process. Already the country’s national security adviser, he had been deputising for Heywood and, having worked with Theresa May for several years, the 54-year-old was someone May felt she could trust. Unlike all but one of his predecessors, Sedwill had never worked at the Treasury, although he holds a masters in economics from Oxford. “Mine is an unusual background for cabinet secretary, having spent much of my career overseas in security and international roles,” he said recently.



Sedwill rose up through the Diplomatic Service, becoming Britain’s ambassador to Afghanistan in 2009 and Nato’s representative in the conflict-ridden country a year later. There were also spells in the Home Office before he became permanent secretary there at what was May’s department in 2013.

Ministerial advisers say his background means he has little patience for leaks, currently running at epidemic rates amid the constant rowing about Brexit. “He just doesn’t understand why anybody would leak, whereas Heywood would see it as an occasional occupational hazard,” one said.



Some even believe Sedwill has been looking for the opportunity to prosecute a leaker, with regular cabinet papers marked secret so they would be covered under the Official Secrets Act, meaning that any leaks could potentially be a criminal offence.



The sharply worded letter he sent to the senior ministers who sit on the National Security Council on 25 April 2019 made clear that immediate cooperation with the forthcoming inquiry was expected. As a result of his investigations, Gavin Williamson was sacked as defence secretary.

Dan Sabbagh, Defence and security editor Photograph: HoC

Jeremy Hunt, the foreign secretary, was the first to go public on Thursday in denying he was behind the leak, condemning it at a lunch of the parliamentary press gallery. He said it was was “utterly appalling” and said denied that he or any of his staff were involved.

The leadership candidate added: “I – as I think everyone here knows – have never leaked confidential cabinet discussions and I never will, so I don’t want to comment further. But I do think it is a very, very bad day for our democratic processes.”

Shortly after, Gavin Williamson, the defence secretary, released his own statement of denial. He said: “Neither I nor any of my team have divulged information from the National Security Council.”

Sources close to Penny Mordaunt, the development secretary, then said she “categorically denied” being involved in the leak – a statement that was echoed shortly after by allies of the trade secretary Liam Fox.

Finally, Sajid Javid, the home secretary, and another leadership contender, denied being involved. He also said: “For any cabinet minister or any minister in the government to share sensitive information in the public domain is completely unacceptable and it should be looked at.”

Facebook Twitter Pinterest Jeremy Hunt and Gavin Williamson leaving Downing Street. Both have denied leaking details of the NSC meeting. Photograph: Toby Melville/Reuters

Sedwill’s inquiry began with a letter to the members of the NSC – a secret official body comprising the prime minister, nine cabinet members, spy chiefs and senior members of the armed forces. Phone and email records could be examined and people questioned if it develops further and even lead to a minister or aide being fired.

Former cabinet secretary Gus O’Donnell, who helped set up the NSC, said the leak was “incredibly serious” and a “complete outrage”. “If I were cabinet secretary and I thoroughly applaud what my successor Mark Sedwill has done is to say ‘look, this is just beyond the pale’ - this is really important for the country, these issues are massively important,” he told BBC Radio 4’s Today programme.

Former defence secretary Michael Fallon said on Thursday that Downing Street should call in the police and mount a “a proper Scotland Yard investigation” and Andrew Mitchell, the Tory MP for Sutton Coldfield, told the BBC’s Newsnight that MI5 should be asked to help.

Q&A What is Huawei and why is its role in 5G so controversial? Show Hide Fast-growing Huawei is arguably China’s first global multinational. The Shenzhen-based company makes mobile phones, base stations and the intelligent routers that facilitate communications around the world. But its success increasingly concerns the US, which argues Huawei is ultimately beholden to the Chinese Communist party and has the capability to engage in covert surveillance where its equipment is used. Huawei is by some distance the world’s largest supplier of telecoms equipment with an estimated 28% market share in 2019. It was also the second largest phone maker in 2019, after Samsung and ahead of Apple. But Australia banned Huawei from 5G in 2018, with its spy agencies declaring they were worried the company could shut down power networks and other parts of its infrastructure in a diplomatic crisis. Trump banned US companies from working with Huawei last year and has strenuously lobbied others to follow suit, venting “apoplectic fury” in a phone call to Boris Johnson after the UK agreed to allow the Chinese company into 5G. The company had successfully targeted the UK early on. It has supplied BT since 2003 and gradually expanded to the point where it agreed to create a special unit in Banbury, known as the Cell, where the spy agency GCHQ could review and monitor its software code. Vodafone is another key customer. Britain’s intelligence agencies said in January that any Huawei risk could be managed as long as the company was not allowed to have a monopoly. As a result, Boris Johnson concluded Huawei’s market share should be capped at 35% for forthcoming high-speed 5G networks. In July 2020 the UK position changed, and it was announced that Huawei is to be stripped out of Britain’s 5G phone networks by 2027. Oliver Dowden, the UK culture secretary, also announced that no new Huawei 5G kit can be bought after 31 December 2020 – but said that older 2G, 3G and 4G kit can remain until it is no longer needed. Dan Sabbagh Defence and security editor Photograph: Mark Schiefelbein/AP

No 10 reacted with anger and alarm after the Huawei decision was leaked. It follows a series of leaks from cabinet and other sensitive political meetings as May’s authority has collapsed during the Brexit crisis, but none from the NSC. Insiders said it is a place where “politicians, intelligence agencies and military chiefs are supposed to be able to discuss issues openly and informally”, saying that the leak has eroded trust.

Politicians present had been deadlocked at five apiece, with the decision only being made after what amounted to a casting vote from the prime minister. Those who spoke against the plan argued for a blanket ban on Huawei telecoms equipment.

A public announcement of the decision had not been due for several weeks, after further work was undertaken on various additional safeguards, but the leak transformed the debate with several backbench Conservatives raising concerns on Wednesday and Thursday.

The five ministers in favour of allowing Huawei to supply equipment to “non core” parts of the network, such as antennas, were led by May but also included David Lidington, the Cabinet Office minister, Philip Hammond, the chancellor, Greg Clark, the business secretary, and Jeremy Wright, the culture secretary.

The Guardian view on Huawei: if May wants to trust, we must keep verifying | Editorial Read more

It is understood that the final decision was in line with the advice from Britain’s intelligence agencies, led by GCHQ’s National Cyber Security Centre, which already monitors Huawei technology in case of a backdoor that could be exploited by the Chinese government.

The spy agency has repeatedly said Huawei must be monitored but that the risks can be contained. But politicians concerned about the company said the UK should heed warnings from US and Australian spy agencies, who share intelligence with the UK as part of the Five Eyes network.

Tom Tugendhat, the chair of the foreign affairs select committee, told MPs: “This is fundamentally a diplomatic and political question, just as much as a technical one, and … respecting our Five Eyes partners is an essential part of the decision.”

Earlier Labour demanded “a full leak inquiry” in an urgent question in the House of Commons. Jo Platt, the shadow minister for the Cabinet Office, said: “If a minister did leak this information they are not fit to serve in the cabinet and they are certainly not fit to be prime minister.”

In the debate that followed, Wright condemned the leak and signalled that a criminal investigation under the Official Secrets Act could yet go ahead. He told MPs “I cannot rule it out”, and added it was “a matter for investigating and prosecuting authorities to consider”.

Hammond is in China to participate in an investment forum in Bejing. On Thursday he met Hu Chunhua, the country’s vice-premier, but it is understood that the subject of Huawei was not raised by either side.