By Justin Parkinson BBC News Online at the NUT conference in Harrogate

The National Union of Teachers - with 250,000 members - is the only one of the big education unions in England and Wales officially opposed to the government's workload agreement.

Under the agreement, so-called "higher-level" teaching assistants will be allowed to teach classes.

Called "historic" by the government, its aim is to allow more time for lesson preparation and marking while reducing the amount of administrative tasks.

The other major unions signed up to the agreement in January.

Jim Warner: "The government is saving money"

But the vast majority of NUT members at the annual conference in Harrogate, North Yorkshire, are opposed.

Jim Warner, a teacher from Dudley, West Midlands, said: "Teaching assistants will be allowed to take classes, but this will be under the supervision of a teacher.

"The teacher has to prepare the lesson plan and supervise. It's not a reduction of workload.

"The government is saving money. It is getting the job done by lower-paid workers.

"We believe that the teaching assistants are a valuable part of our support in the classroom. They are not paid well enough for that.

"We have been arguing that teaching is a graduate profession.

"It's a skill that needs development and training. The children themselves are the ones who are not going to get the professionalism of a fully trained teacher."

Alison Long says it is unfair on the assistants

Alison Long, a secondary school teacher from Lewisham, south-east London, added: "It's the assumption that teaching is something that you can just pick up in a few minutes that annoys us.

"We need the skills and knowledge to work with what the children have given us.

"Teaching assistants do an enormous amount of good work with individual children.

"They support teaching. For instance, if someone needs help with literacy, they will sit with the child and take them through it.

"But teaching is not what they are trained to do. It's completely unfair on them, that they should be asked to take a whole class for just �7 an hour.

"It's all just a money-saving exercise by the government."