Image copyright Reuters

The Defence Secretary has reportedly said he has "very deep concerns" about Chinese firm Huawei being involved in upgrading the UK's mobile network.

Gavin Williamson's comments - reported by the Times - came after some nations restricted use of the firm's products in 5G networks over security concerns.

MI6's head recently said Britain faced decisions on Chinese ownership of tech.

The UK says China is behind hackers targeting commercial secrets. Huawei denies any link to the Chinese state.

On Wednesday, Mr Williamson was reported as saying: "I have grave, very deep concerns about Huawei providing the 5G network in Britain. It's something we'd have to look at very closely."

Australia, New Zealand and the US have restricted use of Huawei technology in 5G mobile networks, and Mr Williamson said the UK would look at their example.

"We've got to recognise the fact, as has been recently exposed, that the Chinese state does sometimes act in a malign way," he added.

Huawei was founded by a former officer in the People's Liberation Army but the company denies having any ties to the Chinese government, beyond complying with tax laws.

The firm has strongly rejected any suggestion that it poses a security threat, saying it has "never been asked by any government to build any backdoors or interrupt any networks".

Earlier this month, MI6 chief Alex Younger said the UK needed to "decide the extent to which we are going to be comfortable with Chinese ownership of these technologies".

UK communications company BT has already said it is removing Huawei equipment from its 3G and 4G networks, and pledged not to use the firm's products in the "core" of its 5G service.

'Cyber intrusions'

This week it confirmed that Huawei equipment was being removed from the heart of a communication system being developed for the UK emergency services, although it was not explicit as to why.

On 20 December, the US indicted two Chinese men accused of hacking into computer networks of Western companies and government agencies, and accused Beijing of cyber-spying.

UK Foreign Secretary Jeremy Hunt described the men's actions as "one of the most significant and widespread cyber intrusions against the UK and allies uncovered to date".

The Foreign Office said hackers acting on behalf of the Chinese Ministry of State Security were stealing commercial secrets from firms in Europe, Asia and the US.

Officials said their activities were so extensive, they were "putting at risk" economic growth in the UK and the wider global economy.