Disgruntled headteachers could take industrial action after they voted overwhelmingly against schools being forced to become academies.

A motion that "no schools should be forced to become an academy" at the National Association of Head Teachers (NAHT) annual conference in Birmingham was passed by a majority of 95%.

The motion was amended to include a "last resort" move that instructed the association's national executive to "consider all options open to NAHT up to and including as a last resort industrial action to ensure the defence of our comprehensive state education system".

Education secretary Nicky Morgan told the conference on Saturday morning, ahead of the motion, that she would go ahead with her reform plans because she believed academies "make it easier to spread the reach of the best leaders over several schools".

She attempted to alleviate the headteachers' concerns about the proposals by telling the conference that "no good rural school will close as a result of this policy".

But her speech did little to lessen opposition to the proposals, as delegates at the conference made a last minute amendment to a motion to include industrial action.