Contractors could be forced to seek permits for workers they hire from the countries joining the European Union in May.
A decision whether to go ahead with a permit plan will be taken on Monday. Any move would be part of the government's attempt to reconcile popular fears of unrestricted migration with contractors' need for labour.

It is also expected that ministers will tighten the "habitual residence" rule that prevents workers seeking unemployment benefit within a specified period. Currently, the limit is six months, but it could be extended to 18 months or two years.

Both measures may be introduced only if immigrant numbers exceed the 12,000 to 13,000 a year that is anticipated by the Home Office, or if UK unemployment begins to rise.

The migration controversy was heightened this week when the Dutch parliament voted to remove 26,000 failed asylum seekers within three years, even though many of had settled down and started families after being in the country for up to a decade.