The sixth form version of the courses, which are being launched next year, will count as 3.5 A-levels for both league tables and university entrance purposes.

And at key stage 4, pupils taking the mid-level “higher” diploma will gain the equivalent of seven GCSEs at A*-C, as revealed in The TES last month.

Ministers also announced that pound;45 million would be made available to train staff to teach the diplomas in 2008-9, while schools and colleges will be given a share of pound;28 million, equal to an extra pound;1,000 per diploma student.

The ratings by the Government were based on recommendations from the Qualifications and Curriculum Authority and the Universities and Colleges Admissions Service.

John Dunford, general secretary of the Association of School and College Leaders, said they would give a big boost to diploma take-up. He agreed with the level of study required and the commitment students would need to gain the diplomas.

But some are not convinced. The Daily Mail pointed out that the advanced hair and beauty diploma being introduced in 2009 would be worth more than A-levels in maths, physics and chemistry. At higher level, pupils are broadly expected to spend three days a week studying for the diploma, suggesting that the seven GCSE equivalence is on the high side.

However, there may be a catch. Pupils will need to pass all four main elements of the diploma to pass overall. It is unclear whether those failing one of the four elements - functional skills, additional and specialist learning, principal learning and the extended project - will gain league table credit.

At the lowest level, foundation, a diploma will count as five GCSEs at A*-G.

Alan Smithers, professor of education at the University of Buckingham, said the equivalences were inflated.

He said he was worried that pupils might be pushed towards diplomas by schools concerned to improve their league table positions, but that young people might find employers and universities did not value them.

FOUR TYPES OF DIPLOMA

Foundation - Takes roughly same time as four to five GCSEs. Worth five GCSE grades A*-G.

Higher - Takes roughly same time as seven GCSEs. Worth seven grades A*-C.

Advanced - Takes roughly same time as three A-levels. Worth 3.5 A-levels.

Progression - Takes roughly same time as two A-levels. Equivalence not yet announced.

Diplomas in 17 subjects will be introduced between 2008 and 2013.