Ministers faced fresh calls to scrap A levels yesterday - just 48 hours before 250,000 teenagers receive their exam results.
The centre-left Institute for Public Policy Research think-tank called for a new "British baccalaureate" diploma to be introduced, with A levels "phased out" from 2008.
The baccalaureate should cover both academic courses and work experie nce and would help address the UK's high drop-out rates among 16 and 17-year-olds, IPPR said.
Last year the Government rejected similar recommendations from former chief schools inspector Sir Mike Tomlinson to replace GCSEs and A levels with a diploma.
Tony Blair insisted that A levels would stay and Ministers announced plans for a set of mainly vocational diplomas to run a longside traditional qualifications.
The Government promised at the time to review the situation regarding A levels in 2008.
Richard Brooks, IPPR's associate director, said the Government's proposals were unlikely to succeed.
"Practically all young people in the UK should now be in education or training until they are 18 or 19 years-old," he said.
"Not only are too many still missing out but current policies don't seem to be increasing the numbers of those who stay on in learning until the end of their teenage years.
"The new 14-19 diplomas will not flourish alongside an un-reformed system of A levels and it is time for a more radical approach."
A spokeswoman for the Department for Education and Skills rejected the think-tank's calls.
"Our position has not changed. A levels are here to stay," she said.
Sixth-formers across the country will receive their A level results tomorrow.