The largest teaching union, the NUT, ended its conference with votes backing a "rolling programme of industrial action".

Delegates defied union leaders to call for an immediate £2000 pay increase and a boycott of cover for absent colleagues, a move that could lead to a four-day week in some schools.

Elsewhere at the NASUWT conference in Scarborough, education minister Stephen Timms set out a new working contract for 500,000 teachers, including a "meaningful guarantee" of professional time spent working out of the classroom.

NASUWT leaders called on the government to create a new serious offence of assaulting a public service worker.