The website is undermining the Construction Plant Competence Scheme (CPCS) which covers thousands of machinery operators across the industry.

It is relied on by contractors to prove that operators are qualified to drive kit like excavators and dumper trucks.

A website started-up early this year based in Romania selling the right answers to the theory part of the tests for less that than £10.

Scheme owners the CITB have shut down three versions of the site but another has now sprung-up.

Ian Sidney, Fraud Investigator at the CITB, said: “Despite continuing efforts, it’s proving tricky to put a stop to these illegal websites – but we won’t be deterred.

“Three websites have already been shut down as a result of the CITB Fraud Squad’s efforts, but a fourth has been opened under a different domain name.

“We are working with our solicitors and looking at other options to have those responsible cease and desist.

“The process is lengthy but we are determined to stop fraudsters from bringing the industry into disrepute and putting lives at risk.”