The Specialist Engineering Contractors (SEC) Group has written to prime minister Gordon Brown to demand that public sector contracts be awarded only to firms that invest in training.

Rudi Klein, the SEC Group’s chief executive, said it was unfair that companies using reputable licensing schemes could be passed over by the public sector in favour of cheaper alternatives.

He said: “The public sector gives work to people who put in a low price, but who don’t train. They must work with people who have reputable schemes, or that can demonstrate, independently, they can deliver the necessary quality.”

The public sector is responsible for 40% of construction spending.