One of five cabinet ministers who spoke out in opposition to plans to allow the Chinese telecoms firm Huawei to help build the UK’s 5G network at Tuesday’s tense meeting of the National Security Council (NSC) were being touted as the most likely source of a destabilising leak. As an inquiry led by the cabinet secretary, Sir Mark Sedwill, began on Thursday, all five were rushing to categorically deny it could have been them. But, despite the denials, could one of them have been behind the disclosure?

Gavin Williamson

The defence secretary was being named – without any back-up evidence – by several Conservative MPs after the leak, but pushed back hard, saying: “Neither I nor any of my team have divulged information from the National Security Council.” The former chief whip has a reputation as an intriguer and wants to be a kingmaker in the upcoming leadership contest. He will also be well aware of the concern about Huawei in some parts of the intelligence community, but ought to know, because of his remit, the dangers of leaking from the NSC.

Jeremy Hunt

Facebook Twitter Pinterest Photograph: Daniel Leal-Olivas/AFP/Getty Images

The foreign secretary and leadership frontrunner is usually seen as the typical safe pair of hands, but knows he needs to tack to the right to pick up support across all levels of the party and has made some uncharacteristic misjudgments in recent months, for example when he compared the EU to the old Soviet Union. Leaking his opposition to even allowing Huawei on to the fringes of the 5G phone network might have been thought to help that cause. But on Thursday, as he denied any involvement, he was emphasising he was not a noted leaker: “I – as I think everyone here knows – have never leaked confidential cabinet discussions and I never will.”

Sajid Javid

The home secretary may harbour leadership ambitions, but his campaign is struggling. Like Hunt he knows he has to woo rightwing support, but previous efforts – most notably the decision to strip Shamima Begum of her UK citizenship – have gone too far. As one of the more tribal Tories, he likes to stay close to rightwing newspapers such as the Daily Telegraph, where the leak first appeared, and faced with a campaign losing momentum a leak may have been attractive. But as home secretary he will be acutely aware of the importance of classified information, saying on Thursday: “For any cabinet minister, or any minister in the government, to share sensitive information in the public domain is completely unacceptable.”

Liam Fox

The international trade secretary is the only one of the five who is not running for the leadership, although his willingness to stay on in cabinet when several other Brexiters have quit suggests he is keen to remain in high office. As a former defence secretary, Fox has strong defence contacts on both sides of the Atlantic, and would well understand the importance of the NSC. It is possible he could be motivated by strong feelings about Huawei, but Fox also knows what it is like to lose ministerial office: he was forced to resign as as defence secretary in 2011. Sources close to Fox were categorically denying his involvement on Thursday.

Penny Mordaunt

Facebook Twitter Pinterest Photograph: Isabel Infantes/AFP/Getty Images

The development secretary still has leadership ambitions, although is not considered a frontrunner, and in any event is eager to advance in cabinet, possibly to become the UK’s first female defence secretary. That might be considered enough to justify a leak, although Mordaunt comes from a military family and is a naval reservist, considering herself particularly loyal to Britain’s armed forces. As with Fox, sources close to Mordaunt, aware of the seriousness of the situation, were categorically denying on Thursday that she had been involved in the leak.