Sixth formers should be forced to study maths beyond the age of 16 as part of the Government's new diploma qualifications.
The Advisory Committee on Mathematics Education said without this safeguard the diploma's introduction could make it even harder for universities to find maths and science undergraduates.
The committee said: "The current and likely detailed mathematical requirements in diploma design run the serious risk of reducing rather than increasing mathematical competence at all levels."
Diplomas are being trialled in five work-related subjects from September. By 2013, they will be available in 17 subjects at three levels to all 14- to 19-year-olds.
Under the committee's proposals, all post-16 diploma students would have to take at least a higher level functional skills qualification in maths.
Those studying for an advanced diploma in a maths-related discipline would be required to study the subject at the equivalent of AS level.
The committee operates under the auspices of the Royal Society and is a bridge between maths teachers and the Government. Its paper points out that in most other developed economies, students have to study maths to 18.
The committee said GCSE maths was increasingly viewed as inadequate preparation for most higher education courses.
It added that those without post-16 maths were losing university places to European Union students, or those who had taken the International Baccalaureate.
The committee is also concerned that diplomas in subjects perceived to be less numerical, such as humanities or languages, might have little mathematical content.
Professor Madeleine Atkins, vice-chancellor of Coventry University, this week told MPs that the range of topics studied for maths A-level had increased in recent years. "But there is less depth, particularly in calculus," she said.
There was a need for numeracy across many vocational fields, including nursing, for which students had often dropped the subject at 16.
Professor Atkins added: "They arrive to learn about drug medication and they can't quite remember which bit to put above which bit when calculating percentages. That's quite worrying."