One West Country plant hirer reported that he asked his instructor to leave the site after fearing he might damage the equipment or hurt himself.
The hirer needed a CPCS card for his dragline operator, as the firm had moved from working its own quarry to seeking external work.
The hire boss said: 'My operator has been working the rope-operated dragline for 45 years and is faultless, but we had never needed a ticket before now.
'The guy the CITB sent out to write the tickets could not drive the machine - he couldn't even operate the boom.
'I told him the best he could do was to get off the site quick. I reckon for an instructor to be any good on something like a dragline you need to be about 50, but he couldn't have been more than 19 years old.'
The sentiment was echoed by operators in other parts of the country.
One north-eastern operator said: 'We had a safety manager on one site who retrained as an instructor. He now has a wallet full of cards, but he cannot operate the kit. He certainly can't have the necessary experience.'
At the same time, operators have warned that the cost of reassessment and new cards is in danger of driving out skilled workers and creating a skills shortage.
Scottish operator John McIver said: 'We recently had some work with a D6 dozer but it took three drivers before we got someone who could really operate it well. He was 67 years old.'
Mr McIver reckons the CPCS card renewal scheme has made it too expensive for many older drivers to retain their -categories. He said: 'There are people coming out of training colleges such as Bircham Newton with loads of categories. It is heartbreaking for people with experience who are unable to get on the tools because they no longer have the accepted training for their -categories.'
Yorkshire operator John Taylor said that the number of different cards for different sectors was adding to the -difficulties.
He said: 'I have tickets that allow me to work in construction, engineering construction, to move nuclear fuel and to drive HGVs for the Army, but I have just been told that I can't work for my employer in a quarry without an EPIC card.'
Mr Taylor has been quoted a fee of £2,500 to train and acquire the card.
He said: 'It is no wonder there is a skills shortage. This sort of jumping through hoops is not improving the industry - accidents are still happening.'