Four companies issued with warnings over failures in fire safety at Hinkley Point C have made improvements at the request of the nuclear watchdog.

The Office for Nuclear Regulation (ONR) said licensee NNB Generation Company and contractor REEL had complied with the enforcement notices handed to them.

The ONR identified the breaches after pre-planned inspections at the Somerset nuclear plant in November last year. The regulator said improvements were required to address the shortfalls in compliance and prevent reoccurrence.

A further two notices were served at the time to contractors Bouygues Travaux Publics SAS and Laing O’Rourke Construction – the joint venture partners in BYLOR JV. These warnings were resolved in April 2024, the ONR said.

According to French-owned energy giant EDF, Hinkley Point C nuclear plant will provide six million homes with low-carbon energy once it is built.

But the Bridgwater nuclear project has been dogged by delays and spiralling costs, with EDF admitting in Januarythe project was likely to take another four years to complete and have a final price tag of around £35bn. When construction started in 2016, the it was estimated to cost £18bn.

France’s state-owned energy operator originally hoped to complete the power station in 2027, but has now said it could be as late as 2031.

In July, bosses released a video of the project’s progress. The footage shows preparations to install the first nuclear reactor, the massive steam generators and the world’s largest turbine. It follows last year’s ‘dome lift’, when the reactor building roof was hoisted into place.

The news comes as questions continue to be raised over who will foot the mounting bill for Britain’s flagship nuclear project. The British government has signalled it will not use taxpayers’ money to pay for overrunning costs despite reports France is pushing for additional support on the scheme.