Some colleges have only received enough funding for bursaries to offer a maximum of pound;200 a year to the poorest students - a quarter of the amount promised by the education secretary.
A snapshot survey of some of the largest colleges found that the new bursaries for college students are on average worth only half of the full education maintenance allowance (EMA) at pound;633 a year. The University and College Union (UCU) survey of the 51 largest colleges found that most had still not published any details of the bursaries available to teenagers enrolling in courses for September.
Among the 14 which had set out their plans, the maximum bursary ranged from a maximum of pound;1,200 in some colleges to a low of just pound;200.
Education secretary Michael Gove said the bursaries had sufficient funding to allow colleges and schools to offer pound;800 a year to students with a family income of pound;16,190 or less.
But FE Focus reported in June that the allocations appear to have penalised FE colleges which have large numbers of one-year students, and therefore do not attract the Government's transitional funding for the EMA.
As a result, several colleges appear to have calculated that their allocations will only allow them to fund much lower maximum bursaries.
At Richmond-on-Thames College, students with family incomes below pound;16,190 can only claim pound;340 a year, and at Derby College the maximum is pound;200 a year.
The UCU said colleges had been placed in a difficult situation where they had little notice of the new scheme or the funding they were likely to expect, and had to design their own eligibility criteria.
UCU general secretary Sally Hunt said: "What is clear is that the poorest students will not receive the money so many say is vital to staying in education.
"The EMA was a successful scheme that helped young people stay in education and the Government was completely wrong to scrap it, particularly without having given any thought to what may replace it."