The scheme replacing the education maintenance allowance (EMA) is pound;200 million short of the bare minimum needed to support the poorest students, colleges have warned.
After thousands of students and teachers took part in Monday's national day of protest against the scrapping of the EMA, the 157 Group of leading FE colleges has calculated that a bottom line of pound;225 million per year is needed to help students from deprived backgrounds to stay in education.
The Government's learner support fund, which will replace the EMA, currently has a budget of pound;26 million - 12 per cent of what the 157 Group says is the absolute minimum required - rising to pound;78 million, just 35 per cent of the colleges' benchmark, in 2014.
The Department for Education this week described the EMA, which costs pound;560 million a year, as "an expensive programme that only increased the participation in education of a minority of students", and vowed to target support only "at those students who really need it".
But Lynne Sedgmore, the 157 Group's executive director, said: "The pound;225 million per year is the minimum we feel must be put in place for supporting disadvantaged students if the system is not to be seriously destabilised.
"The Coalition intends to give more `targeted support' in place of EMAs; it could do so by targeting the poorest 25 per cent, or lowest quartile, of 16-18 students. This would mean an extra pound;200 million is required in the learner support funds as a minimum."
The figure was calculated on the basis that the poorest 300,000 students receive an average bursary of pound;750, amounting to pound;25 per week for 30 weeks of term.
The 157 Group favours phasing out the EMA gradually by providing at least pound;550 million for existing and new learners in 201011, and pound;275 million extra for 201112 to see students through two-year courses.
Meanwhile, dozens of colleges have this week been using the dregs of this year's EMA funding to try to attract students to new courses starting in January, promoting them as a "last chance" to claim the allowance, worth up to pound;30 a week.
One college leader told The TES: "Colleges are trying to get in the maximum numbers they can, as next year's funding is based on this year's figures. It's a huge challenge to keep these students once the EMA runs out."
Julian Gravatt, assistant chief executive of the Association of Colleges, said: "It makes sense that there is a push to get people to sign up, considering (the EMA) is going to go with not much notice."