Client EDF has confirmed the targeted start of electricity generation has been pushed back to June 2027 while final construction costs are estimated at between £25bn and £26bn.

Stuart Crooks, Managing director of Hinkley Point C said in a message: “You will all have experienced the severe impact of Covid-19 on the project over the last two years. You will remember how we suddenly had to cut numbers on site from more than 5,000 to around 1,500.

“For many months after that, we remained far below our plan for site numbers as our ability to fully ramp up activity was thwarted by the need for measures to prevent infection.

“Keeping workers safe with social distancing in canteens, buses and at work meant we had no choice but to become less efficient. In civil construction alone, having fewer people than planned means we lost in excess of half a million individual days of critical work in 2020 and 2021.

“Our supply chain was also hit hard and is still impacted now. In April 2020, 180 suppliers were fully shut down, but even as late as February this year, more than 60 suppliers were operating with reduced productivity due to Covid.”

Crooks said that in January 2021, EDF estimated a six-month Covid impact, assuming an imminent return to normal conditions, but the second second wave of Covid-19 stopped that happening.

He added: “In total, the start date for Unit 1 has gone back 18 months since construction started in 2016. In such a complex project, it wouldn’t be credible to say we can measure exactly how much of this is due to Covid-19 impact, but it is clearly in excess of 12 months.

“Other factors have affected the schedule and costs.

“Marine works have also cost more, although they are now in a good position – with legal hurdles finally cleared to allow the team to get on with the job.

“Running the site for longer and less efficiently during the pandemic also adds cost. We are facing the same issues as other major projects with UK-wide supply and labour shortages and inflation.”