The government has written to the likes of O2, Vodafone and EE to say that phone networks should be careful over which companies they choose as suppliers when building their 5G networks.
The entire supply chain may be disrupted by an ongoing review of the UK's telecoms infrastructure, according to a letter penned by the Department for Digital, Culture, Media and Sport's (DCMS) head of digital policy Matthew Gould, and the National Cyber Security Centre's (NCSC) CEO Ciaran Martin.
The Future Telecoms Infrastructure Review, launched in July, aims to ensure that Britain's "critical national infrastructure remains resilient and secure", according to the letter seen by the Financial Times (FT).
The letter said the "outcome of the review may lead to changes in the current rules" and that the firms "will need to take the review into consideration in any procurement decisions".
Analysts suggest the letter is directed at a handful of Chinese manufacturers, such as Huawei and ZTE, which may be barred from the 5G process altogether over national security concerns.
Just as the government announced its major infrastructure review, an advisory board partly-led by the NCSC declared Huawei's hardware may pose a risk to national security.
The Huawei Cyber Security Evaluation Centre (HCSEC), which is owned by Huawei and overseen by the UK's national security agencies, revealed in its annual report that shortcomings in the engineering process have "exposed new risks" to UK networks.
"The Oversight Board can provide only limited assurance that any risks to UK national security from Huawei's involvement in the UK's critical networks have been sufficiently mitigated," the report said.
These concerns are disputed by the companies but were prominent enough for the Australian government to this summer institute a ban of Huawei and ZTE from providing 5G technology in the country.
Despite the government's warning, the telecoms industry is already well underway in the building and testing of 5G infrastructure. For instance late last month Vodafone activated its first 5G trial in Salford, Manchester.
Rival firms have also made serious headway in building their own 5G infrastructure with help from Chinese manufacturers, with Huawei considered integral to the future Three 5G network, and BT's 5G outlay.
Paolo Pescatore, senior vice president of consumer services at MIDiA Research, told IT Pro the government's warning has arguably come too late - as network providers have already announced trials with their partners.
"Yes, this does seem to be directed at Huawei," he said, "but in reality telcos have few options when choosing a network provider due to consolidation.
"5G represents a pivotal point for all countries and it is important to get the right framework for the future.
"Other nations have shown concerns around security so it is something that should be carefully considered. Despite this, Huawei has so far proved to be a credible partner for telcos around the world."
