The decision came in April after the utility sought advice from the National Cyber Security Centre, a branch of the nation’s signals intelligence agency GCHQ, the newspaper quoted a Whitehall official as saying.

National Grid declined to comment, citing “confidential contractual matters”. “We take the security of our infrastructure very seriously, and have effective controls in place to protect our employees and critical assets to ensure we can continue to reliably, safely, and securely transmit electricity”, it said in a statement.

The FT said an employee at the Nari subsidiary NR Electric UK had said the company no longer had access to sites where the components were installed and that National Grid did not disclose a reason for terminating the contracts.

It quoted another person it did not name as saying the decision was based on NR Electric UK components that help control and balance the grid and minimise the risk of blackouts.

It was unclear whether the components remained in the electricity transmission network, the report said.

NR Electric UK, GCHQ, and the Chinese embassy in London did not immediately respond to Reuters requests for comment outside business hours.

The UK’s department for energy security and net zero said that it did not comment on the individual business decisions taken by private organisations. “As a government department we work closely with the private sector to safeguard our national security,” it said in a statement.