The National Union of Teachers has refused to join the Government-led rewards and incentives group (Rig), since rejecting the workload deal that gave teachers more time outside the classroom to plan lessons, three years ago.

The NUT will criticise the power of the Rig - which brings together ministers, local authorities and unions - and call for a new bargaining group to replace it.

The NUT has been punished for staying out of the so-called social partnership. It was excluded from a review into personalised learning which includes the GMB and TG support staff unions, yet was consulted over behaviour measures in the recent education bill. Steve Sinnott, the union’s general secretary, called the consultation process “completely arbitrary”.

The NASUWT leadership has been attacked by some of its members for getting too close to the Government.

But Brian Garvey, its president, rejected the accusations, saying that, without the workload deal, teachers would not have won time for marking and lesson planning.

He quoted Eileen Halls, a teacher from Wakefield, who said: “You can put an alien in front of my class as long as I get time to do some work.”

A motion at the ATL conference calling for it to withdraw from the social partnership was overwhelmingly defeated.