Radical reform of the school workforce is key to a £1 billion investment plan for education, David Miliband has said.

Speaking to an education conference in Warrington on Wednesday, the schools minister told delegates that "teachers should never struggle on their own".

And he warned teaching unions not to "miss the bus" on reforms linked to extra cash.

"We must ensure that teachers work together, work with other adults, and work with new technology, to crack problems in teaching practice," he said.

"No teacher should ever feel on their own when it comes to lesson planning, dealing with unruly pupils, organising the class to ensure there is individual attention. But this vision of teaching requires a step-change in professional practice."

Miliband stressed that he was "committed to an expanding, better paid, and better supported teaching force" .

"But I also know it makes no sense for the teaching profession to be untouched by the breakdown in demarcations, and by the development of front-line flexibility, that is the basis of effective service across the public and private sectors."

Education ministers have "made radical proposals for reform of the teachers' contract, for remodelling of the school workforce, and for cutting bureaucracy - with a team of independent heads and professionals from schools brought in to lead reform".

But the plans have triggered opposition from teaching unions concerned that unqualified assistants may end up supervising classes.

The schools minister repeated assurances that "the clear aim is to cut teachers' workload, reverse the trend towards a smaller and smaller share of the teaching week being devoted to teaching and at the same time raise the quality of the learning experience".

But he highlighted the "key" role of non-teacher classroom assistants.

"The key is make much more use of a wider range of adult expertise, from the learning mentor to the lab technician to the language specialist," Miliband told the conference.

And the minister hit back at teaching union comparisons between classroom assistants, nurses and brain surgeons.

"It is said we should never ask the nurse to do brain surgery. Fair enough. But which surgeon operates without a well-equipped and well-trained nursing team?" asked Miliband.

"I am convinced these proposals are a tremendous opportunity for the teaching force. To realise the vision of more personalised teaching and learning we must embrace the chance to do things differently: different ways of doing admin tasks, different ways of providing cover, different ways of promoting high quality learning, under the leadership of a qualified teacher, but not only using qualified teachers."

Unions and local authorities are currently negotiating a classroom reform package, and Miliband warned teachers not to miss "the bus".

"We are very close to a wide-ranging agreement. I appeal to all those involved to be on the bus of reform, because it is leaving the station and is carrying the nation's teachers and students with it," he cautioned.

The National Union of Teachers welcomed Miliband's support for a "well-equipped and well-trained support team working with the teacher".

"If the minister amends his proposed package on this basis there can be agreement," said NUT chief, Doug McAvoy.

"The NUT will not accept unqualified people having responsibility for whole class teaching as currently proposed by the government."

And McAvoy told Miliband: "It is the NUT's bus which is going in the right direction."

Speaking at the same conference, the Liberal Democrats warned against "masking the shortages by the use of classroom assistants".

The party's education spokesman, Phil Willis, vowed that "if it means a further de-professionalisation of teaching then the Liberal Democrats will oppose it".

"It is a recipe for disaster to believe just anyone can stand in front of today's seven year olds - never mind fifteen year olds - and have control, let alone teach effectively," he said.

Willis suggests a more "imaginative" approach to teacher recruitment to fill classroom staffing gaps.

"Why not allow graduates without a National Curriculum subject degree to train as secondary teachers?," he demanded.

"Every child has a right to be taught by a teacher appropriately trained and qualified for the age experience and aptitude of the young people in their charge."