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.

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.