Criminals are overcharging vulnerable candidates like migrant workers for tests.

Standard industry CITB health and safety tests costing £21 are being charged at £1,000 to some candidates.

Criminals are approaching test centres offering them large amounts of cash to use their facilities and guarantee passes for groups of exploited workers.

The CITB is currently working with the National Crime Agency, police, Home Office Immigration Enforcement and the Gangmasters and Labour Abuse Authority to stamp out the problem.

The Enquirer understands that seven arrests have already been made during the investigation with more to follow.

CITB is also terminating contracts with any test centres found to be acting illegally with organised criminals.

Seven centres are understood to have been suspended this year and nearly 3,000 safety tests revoked.

Ian Sidney, CITB Fraud Manager, said: “The intelligence we are receiving is that the fraudsters are trying hard to capitalise in on a surge in demand caused by the lockdown.

“We know that organised crime infiltrates the testing process to get unskilled, illegal or trafficked people genuine qualifications so they can work in conditions of modern slavery on construction sites.

“This generates vast sums of money, some of which is known to help to finance terrorism and other organised criminality. You can help put a stop to it by getting in touch.”