The move would require a change to teachers' contracts in England and Wales.

Morris: Radical changes to teaching

Ms Morris told the Guardian: "There must be time during the working week when teachers are not in contact with their children, so that they've got space."

The extra time away from the classroom should be used to "prepare lessons almost for individual kids", she said.

A report last month by PricewaterhouseCoopers examining staff workload said primary school teachers had an average of 50 minutes a week away from pupils during their school day.

And secondary school teachers were estimated to have around three hours.

Ms Morris's proposal would require classroom assistants and support staff to undertake more tasks.

She told the newspaper she remained "absolutely opposed" to union demands for a 35-hour week and said teachers would still have to mark pupils' work outside the school day.

More teachers

The Liberal Democrats' education spokesman, Phil Willis MP said he agreed that primary school teachers needed more time away from the classroom to prepare lessons.

But he said there had to be more teachers to make that change possible - not just more classroom assistants.

"We reject the Secretary of State's idea that by allowing classroom assistants to take lessons, whilst asking teachers to prepare and mark them, this is lessening the teacher's load.

"Sadly, by cutting back on recruitment targets for primary school teachers, the Secretary of State has demonstrated yet again that this announcement is more about spin than substance."