Gordon Brown was on Tuesday battling to contain union demands to tighten the law on the use of foreign workers in Britain as he attempts to prove to the rest of the world he is serious about fighting protectionism.

Mr Brown has travelled the world proclaiming the merits of open markets – most recently at the World Economic Forum in Davos – and he has made it the theme of his chairmanship of the G20 group of leading developed and developing countries.