The warning comes from ministers and pressure groups for the disabled following a survey which shows that services for students with profound and complex learning difficulties is "patchy".
But college leaders insist they have done the work needed to meet the "reasonable and realistic" criteria required by the Special Educational Needs and Disability Act. However, they say at least pound;50 million is needed for buildings by 2005 and help is needed with transport costs.
From April, there will be new planning boards to help disabled students coming into FE. Colleges perceived not to offer fair treatment and equal access could be sued.
The full implications of the legislation were spelled out by the lifelong learning minister Margaret Hodge this week. She warned colleges that for the first time they must provide students with profound and complex learning difficulties equal opportunities, access and social inclusion.
"Do not forget that students will be able to seek redress through the courts if they feel they are not getting equality of opportunity and treatment," she said.
She was due to speak at a Learning and Skills Development Agency conference to review the research and spell out the implications of the Act for colleges. But she was kept away by "other ministerial duties," angering college leaders who were expecting answers to questions about costs in advance of Chancellor Gordon Brown's spending review.
A spokesman for Ms Hodge at the conference said there was a duty on the Learning and Skills Council to offer all special needs students personal planning at 16. It must also set up collaborative partnerships between statutory and voluntary agencies.
But a survey of colleges and adult education providers, published this week by the National Bureau for Students with Disabilities (Skill) and Cambridge University's faculty of education, showed that such collaboration was at best patchy.
Their research also showed that there were "wide regional variations in services for people with profound and complex learning difficulties and that inter-agency collaboration often does not take place".
Liz Maudslay, the project director for Skill, said there was now a clear duty on the LSC to fund courses and on colleges to provide equal opportunities for the disabled alongside mainstream students.
"Who is going to be the first college to be sued by a student for not providing access or equal treatment next September?" she said at the conference.
"That ought to concentrate the minds of everybody".
Judith Norrington, curriculum director for the the Association of Colleges, told FE Focus: "We need something between the legal action and the current position, such as an expert panel - something to provide impartial advice to both the student and the college. We cannot anticipate every eventuality."
The association, with the LSC, Department for Education and Skills and the Disability Rights Commission, will shortly publish Rights to Access, a detailed guide to the implications of the Act.
Cambridge University and Skill have also produced an awareness and training pack, while the Learning and Skills Development Agency are disseminating good practice witnessed in their research.