Colleges face being trampled in the stampede of schools opening new sixth forms under the Government’s five-year plan for education, ministers have been warned.

The danger comes from schools which are able to create sixth forms with lower costs compared with self-contained sixth-form colleges which have separate administrative overheads.

While ministers insist they see school sixth forms as part of the post-16 mix, the Sixth Form Coll-eges Forum (SFCF) argues that colleges are at a disadvantage.

The strategy encourages good-quality schools to create sixth forms, which might mean sixth-form colleges with too few students would not be viable.

The SFCF has told Alan Johnson, the minister for lifelong learning, it wants its concerns taken into account in the five-year strategy, as well as the strategic area reviews being carried out around England.

And in a letter to the Education Secretary Charles Clarke, Sue Witham, head of secretariat at the SFCF, said: “Our initial view of the strategy is that, far from encouraging the growth of sixth-form colleges, developments following these guidelines could actually undermine the successful sixth-form college sector.”

The SFCF says it wants to see more sixth-form colleges being established, but believes competition from schools could have the opposite effect.

Both ministers have met the forum, which has pressed for sixth-form colleges to be a seen as an option which should be available in any part of the country.

Schools, she argues, are able to influence their brightest pupils to stay on at 16 instead of going to college.

And, under former Office for Standards in Education chief inspector Mike Tomlinson’s proposals for 14-19, which are expected to encourage early introduction to Level 3 courses for brighter teenagers, schools will be able to hook their pupils into their own sixth-forms from the age of 14, the forum argues.

The SFCF believes the colleges, because of their size, are better-equipped to provide the greater breadth of education proposed by Mr Tomlinson.

Mr Clarke, in a letter to the SFCF, said: “I can understand your concerns that making it easier for schools to add sixth forms might impact adversely on existing successful sixth-form college provision.

“I would, however, emphasise that we will not be instigating a free-for-all.”

He added: “In areas where there are gaps in provision - whether a deficit of places, of quality provision, or a choice of curriculum and learning environment - it will be for local learning and skills councils to bring partners together to jointly agree how the gaps will be filled.”

The SFCF says there are weaknesses in the strategic area reviews being carried out around the country by the Learning and Skills Council.

These were supposed to make sense of the myriad post-16 choices by finding a balance between college and school provision in each locality.

But, says the SFCF, the strategic area reviews are being carried out in different ways in each part of the country.

Even if this process works, it says, the picture could change with the creation of city academies, which can cater for 11 to 18-year-olds and fall outside the review process.