Colleges that tried to meet the Government's September recruitment guarantee will not be reimbursed for enrolling extra teenage students unless under "significant financial strain", the Learning and Skills Council (LSC) has said.
Only institutions that are more than 10 per cent above their recruitment targets will be eligible for "limited" additional funds made available to the funding body by the Department for Children, Schools and Families.
The news emerged as the LSC carried out a stocktake of recruitment in the last month to determine how the recession and the collapse of the youth job market has affected student numbers, with some colleges reporting enrolment up 15 per cent or more on last year.
Officials originally budgeted for no increase this year, as the numbers in the age cohort had fallen, but they announced funding for an extra 55,000 places in April, or a 4 per cent rise. In many areas, it is feared that the demand is exceeding this, but in others demand is thought to have fallen.
David Igoe, chief executive of the forum, said: "There is a real issue about the 10 per cent rule. I would be very surprised if any sixth-form colleges are given additional funds through this mechanism. The argument is that colleges can just in-fill because of their economies of scale. But most colleges are already running full sets because the funding differential with schools means we have to be efficient."
He said this could be of an advantage to small school sixth forms, which could reach an increase of 10 per cent with just a handful of extra students.
Norman Cave, principal of Bournville College in Birmingham, said he had about 130 more 16 to 18-year-old students than last year and expected that figure to rise to 200 by the year's end.
Mr Cave said the funding squeeze could have a knock-on effect on a group not protected by the September guarantee: unemployed students who look for a college course later in the academic year.
"It's about those people who have been let down by the educational system. It puts colleges in a difficult situation about whether they carry on recruiting and the people likely to be at risk are the Neets."
Rob Wye, director of strategy and implementation for young people's learning at the LSC, said that the 1.5 million 16 and 17-year-olds in education was a record figure.
He said: "Ministers said in April that we would keep learner numbers closely under assessment with the Association of School and College Leaders, Association of Colleges and Sixth Form Colleges' Forum to ensure that every learner who wants a place gets one."