Contractors are fuming at the delays which they fear are putting off workers from joining the job.

One site source said: “I’ve worked on virtually every big nuclear site over the last few decades and it still took me eight weeks to get clearance.”

Security checks for site workers are carried out by independent agencies and administered by G4S under an £80m contract awarded by client EDF Energy.

Another source said: “The contractors are up in arms about this because the checks are taking so long.

“The whole process is a complete nightmare as they go through every tiny detail of your work history and background.

“It’s tough as it is getting enough workers to the site but things like this put people off.

“A lot of people hear about the delays and just go off to another job.”

EDF said:“The Government requires people working on nuclear sites to undergo security vetting.

“We’ve heard feedback from our contractors that the process is taking too long and we have been working with the regulator, the Office for Nuclear Regulation to address the issue.

“We have introduced a new level of access in August. For some groups of workers this is reducing the time needed to get clearance to just 24 hours. They will also undergo appropriate site inductions.”

Caroline Blackman, HR director for civils contractor Bouygues Laing O’Rourke said : “This new type of access has transformed the way our workers get onto site and means that you can be at work within days of getting a job rather than weeks.

“It’s a great example of how complex processes can be simplified without compromising standards.”