Ministers want to introduce a credit-based structure, in which all courses are given a rating according to their perceived difficulty and the time needed to teach them.

Students would then be able to use this credit to transfer their achievements in one type of course to another.

The scheme has similarities with US high school courses - through which students build up credit in different subjects to arrive at an overall average grade - and with the Open University’s points system.

The plan, tucked away in a 14-19 education strategy paper published by the Government this week, suggests an attempt to create the single qualifications framework outlined in the 2004 Tomlinson report on 14-19 curriculum and qualifications reform; it could be seen as “Tomlinson by the back door”.

The move was recently recommended to the Government by an advisory group on which Sir Mike Tomlinson was the most prominent member.

Writing in Staying the Course, a book published this month by the Social Market Foundation, Sir Mike predicts his original proposals will become reality because, by 2011, schools will be opting for the diplomas over A-levels and GCSEs as their “qualification of choice”.

“If this can be achieved, then secondary education will have been transformed for all students, and the objectives set out in my 2004 review will have been achieved,” he writes.

The Government’s plans create the possibility of a blurring of the division between academic and vocational exams.

Its strategy paper said: “We believe that moving to a single credit-based framework for all 14-19 qualifications ... could have significant benefits for young learners.

“We plan to put forward more detailed proposals on how we will move 14-19 qualifications on to a credit-based framework, with a view to completing this ... by 2013.”

However, it said that care was needed to ensure that the standing of GCSEs and A-levels was not damaged.

The Qualification and Curriculum Authority (QCA) has been trialling approaches to introduce a credit-based system to vocational courses since 2006.

The Asdan Certificate of Personal Effectiveness awards, already taken by 50,000 pupils, involves them gaining credit after completing 10-hour teaching blocks.

Marius Frank, head of Bedminster Down School in Bristol, said the courses were “tremendously motivating” for pupils because the learning was in bite-sized chunks.

But a QCA paper last year sounded a note of scepticism, warning that achievements in some subjects did not match those in others.

“Caution is urged regarding using credit as a means for forcing academic and vocational pathways together,” it said.

Full details of strategy report, pages 12-13.