Principals fear the Government is planning to sweep away successful vocational qualifications too quickly as it paves the way for new specialised 14-19 diplomas.
The first are to be introduced in schools and colleges in selected areas from 2008 and the aim is that all 14 to 19-year-olds will be able to take them from 2013.
Department for Education and Skills roadshows designed to inform schools and colleges about the diplomas have cast doubt on the future of Btec National qualifications and left principals believing they will be phased out "sooner rather than later", said the Association of Colleges. It wants to see Btec Nationals retained until at least 2015, said Maggie Scott, the AoC's director of learning and quality.
The new diplomas have been described by Alan Johnson, the Education Secretary, as the biggest education reforms in the world.
The reforms are derived from the Tomlinson recommendations for post-14 education. But A-levels have been notably protected - a safeguard widely seen as an attempt to appease the concerns of Middle England - despite his recommendation that they should be abolished.
The AoC argues Btecs have gained a level of respectability normally associated with academic qualifications. The Btec National Diploma is regarded as equivalent to three A-levels and, since 2004, the qualification has attracted UCAS points for university entry.
"Btec Nationals are tried and tested qualifications that are now accepted routes both into higher education and into employment," said Ms Scott.
"The new qualification has to earn its place in the curriculum."
Over the past two decades, 2.6 million people have achieved a Btec qualification and demand for the courses is still strong. Since 2002, the number of students taking Btec Nationals has increased from 86,000 to 140,000.
Edexcel, the Btec awarding body, criticised the "mixed messages" from the Government about the new diplomas and the impact they will have on existing vocational qualifications.
Isabel Sutcliffe, Edexcel's director of qualifications and standards, denied there were plans to phase out Btecs in the short-term. "That's absolutely not the intention of the DfES," she said. "They recognise that it would be foolhardy to remove existing provision until diplomas have proved themselves."
But a DfES spokesman said that from 2013, "14- to 19-year-olds will progressively be taking specialised diplomas, A-levels or apprenticeships only".
He said: "The process of creating these specialised diplomas will need to include a review of existing qualifications. So we would expect the best of those qualifications or units from them to be included within the diplomas."