The National Institute of Adult Continuing Education accuses Education and Employment Secretary Gillian Shephardt of failing in the pledge to maintain adult education since the 1992 Further and Higher Education Act. The Act said colleges must ensure "adequate" provision over 19s.
Tony Uden, deputy director of the NIACE, said: "The Department for Education and Employment should issue a circular clarifying what are the minimum levels of service of education for adults which can be considered adequate in any area."
NIACE, which advises ministers on the effects of adult education policies, has become increasingly hostile since evidence has emerged that provision has deteriorated since the Act.
Its demand will embarrass Mrs Shephard who is to join her Labour shadow, David Blunkett, at a Trades Union Congress conference on adult education in a fortnight.
Both have pledged to set out their parties policies on adult education for the European Year of Lifelong Learning.
The NIACE report, drawing on six years of research into adult participation in education and training, wants the Further Education Funding Council policy of pushing all colleges to an average level of funding to end.
Mr Uden insists it is being done without clear thought for the impact it is having on the different communities served by the colleges.
Ann Risman, principal of Richmond Adult and Community College, which is to become an FE college in August, backed the NIACE call. "I think it is absolutely vital that the DFEE begins to establish what the Act actually means in terms of delivery at local level."
She said the Government put cash for adult education into local authorities' annual grants then slashed back the service to meet cuts targets. "Large tracts of adult education have completely disappeared because of local authority cutbacks."