Scotland's troubled new school curriculum has been thrown into further chaos after teachers overwhelmingly backed protest strikes before the end of the year.

Delegates at the annual meeting of the Educational Institute of Scotland (EIS) teaching union in Perth voted in favour of industrial action over the roll-out of the controversial Curriculum for Excellence (CfE). The development comes less than a year before pupils sit new exams.

They also backed a motion calling for members to be balloted for industrial action over changes to pensions, which could have them working until they are 68.

Neither vote will automatically lead to strike action, with official ballots required in both cases, but their overwhelming support highlights a growing willingness by teachers to take direct action.

The threats come as teachers warned of an unacceptable CfE workload at a time when cuts are reducing the number of support staff, there is a crisis in supply teaching, pensions are being cut and salaries frozen.

It also puts the union on a collision course with Education Secretary Michael Russell, who is speaking at the event today.

Larry Flanagan, general secretary of the EIS, said: "We don't want to disrupt children's learning because this is about improving learning, but the mood of the conference is very serious and there is a very strong expectation these motions will lead to action."

Celia Connolly, from the Glasgow branch of the EIS, told the conference: "There is still a lack of confidence within the membership regarding the delivery of the curriculum, there is still a lack of clear direction and leadership, there is still a lack of consistency across schools and local authorities. The timetable for delivery of resources has not been met... and there is real concern over courses, resources and assessment procedures.

"The result is a huge increase in the workload of our teachers. CfE is being delivered on the goodwill of teachers and we are working excessive hours and trying to manage an unmanageable, burdensome workload."

Mrs Connelly said the most significant change education had seen in a lifetime was taking place at a time of austerity cuts, teachers suffering pay cuts, an attack on pensions and supply shortages.

Charlie McKinnon, also of the Glasgow local association, described CfE as an "out-of-control juggernaut" and blamed the leadership of Mr Russell, accusing him of political expediency rather than acting in the best interests of pupils.

Not all delegates spoke in favour of strike action. Paul Bladworth, from the East Dunbartonshire local association, argued it would send out the wrong message. He said: "I urge you to think very carefully about supporting a motion that says strike action about CfE because it will be read as if you are against CfE."

A Scottish Government spokesman said the EIS had raised legitimate concerns about teacher workload and Mr Russell had been clear that unnecessary paperwork around CfE was unacceptable.

"There are a range of support materials and resources in place to aid teachers with implementation and Education Scotland inspectors have a clear remit to tackle any bureaucracy which detracts from pupil's learning experience," he said.

Eileen Prior, executive director of the Scottish Parent Teacher Council, said: "We note there has been a commitment by Government about cutting through the excessive paperwork and form- filling being demanded of teachers and it would be reasonable to wait and see what this action looks like and the impact it has, before moving to strike action."

Iain Ellis, chairman of the National Parent Forum of Scotland, said: "We do not believe threatening strike action is helpful to anyone."

Billy Hendry, human resources spokesman for councils umbrella body Cosla, said: "CfE is a flagship policy of the Scottish Government councils remain committed to."