But the oversight board doesn't call for banning Huawei from the country's 5G rollout.
A British watchdog monitoring Huawei products warned of security flaws in its networking equipment and suggested they'll be difficult to fix.
The Huawei Cyber Security Evaluation Centre (HCSEC) Oversight Board report, released Thursday, notes that the suspicion-scarred Chinese telecom's approach to software development brings "significantly increased risk to UK operators."
The government-led group also noted that Huawei made "no material progress" in addressing security problems highlighted in its 2018 report and that "it will be difficult to appropriately risk-manage future products."
However, it didn't suggest that Huawei be excluded from Britain's 5G rollout -- that's up to the Department for Digital, Culture, Media and Sport.
Huawei said in an emailed statement that it takes the issues highlighted by the report "very seriously."
"The oversight provided for in our mitigation strategy for Huawei's presence in the UK is arguably the toughest and most rigorous in the world," a company spokesperson wrote. "This report does not, therefore, suggest that the UK networks are more vulnerable than last year."
The report comes as the US pressures its European allies not to adopt Huawei 5G equipment, citing fears that it could be used to spy for China. Earlier this month, the US ambassador to Germany reportedly warned that nation's economics minister to drop Huawei or the US will limit intelligence sharing.
First published at 4:10 a.m. PT.
Update at 4:56 a.m. PT: Adds more details and Huawei statement.