Labour's John Spellar vowed to call "complacent" Treasury Secretary Danny Alexander's bluff yesterday over a construction industry tax dodge now being used to steal cash from teachers and carers.

The Warley MP told the Star how a constituent working as a temp in schools had raised the alarm after being stung by his employer.

The entirely legal scam sees agencies pass people onto another firm's books - dubbed "umbrella" firms by construction union Ucatt - before "costs" and "expenses" are docked from their pay to cover employers' national insurance.