A masters qualification being urged on teachers risks becoming a "Masters in Teaching Lite", the body representing teacher-training universities has warned.
The Masters in Teaching and Learning (MTL) will be available from September next year, when it will be offered first to 3,000 young teachers in the north-west
Ministers expect that, eventually, all teachers will take the part-time three-year courses, to be run jointly by schools and universities.
The Universities Council for the Education of Teachers (UCET), which represents teacher-training institutions, has welcomed the qualification. But it has written to schools minister Andrew Adonis, and Graham Holley, chief executive of the Training and Development Agency for Schools, to urge caution.
It said the course would need to be recognised as a credible masters qualification if it was to have the necessary impact on pupils' learning. "A centrally prescribed qualification lacking in depth and academic rigour would have little if any credibility and only a marginal impact on classroom performance."
James Rogers, UCET executive director, said: "It is essential this does not become a Masters in Teaching Lite. It has to be a proper masters."
He said it was crucial that the course be approved by the Quality Assurance Agency for Higher Education, but it was important it should not be delivered in "ivory towers" by universities operating in isolation from schools.
Mr Holley described the degree as vital in raising standards and narrowing the achievement gap for children and young people. "The radical, new MTL will give us the chance to make a dramatic contribution to further improving the high quality of our teachers."
Ed Balls, the Schools Secretary, promised last week to offer the MTL first to teachers on his list of 638 struggling schools.
The Department for Children, Schools and Familes said the MTL would be validated by universities in the same way as other Masters level qualifications.
Focus on teachers in first five years of job
l The Masters in Teaching and Learning is to be made available initially to teachers in the north-west from September 2009 and rolled out nationally from September 2010.
l Teachers in struggling schools will be first to be offered the course in each region. l The Training and Development Agency for Schools will initially target teachers in the first five years of their careers.
l Teachers will be given some time out of class to study, but will be expected do the rest of the work in their own time.
l About pound;30 million a year is being set aside to pay for teachers' fees. It is not yet clear if this will also cover the cost of schools obtaining supply cover.
l Teachers' association The Voice has warned that staff in their first five years are already under considerable strain. It believes that the qualification should be offered instead to teachers later in their working lives.