Low-skilled migrant construction workers will be allowed to work in the UK only to plug short-term skills gaps under measures outlined by the government this week.
Under the plans announced by Charles Clarke, the home secretary, foreign workers must comply with an Australian-style points system to enter the UK. Low-skilled workers from outside the European Union will be allowed in to solve labour shortages only on specific projects, such as the Olympics.
However, UCATT general secretary Alan Ritchie warned the controls would not prevent unscrupulous employers taking advantage of vulnerable workers.
He said: "Many employers will use informal routes to recruit migrant workers."
The proposals are due to come into force within two years.