And many colleges were unaware of how the Care Standards Act 2000, which came into force in March 2002, affects them, according to a report by the Learning and Skills Development Agency.
The agricultural and horticultural sector is hardest hit by the new laws, which force them to provide separate facilities for under-18s.
The LSDA has called for more funding to ensure learners from poorer backgrounds are not excluded from courses.
Mick Fletcher, research manager at the LSDA, said: "The introduction of the new regulations has clearly led to increased costs. Individual colleges will need to recoup the costs through their fees.
"The Learning and Skills Council and Department for Education and Skills needs to review the allocation of learner support funds so that disadvantaged learners don't lose out."
Julian Gravatt, director of funding and development at the Association of Colleges, said: "We have concerns about the new laws. There are various pressures in the system that are increasing college costs and quite a lot of them come from Government.
"We are asking the Government to back the changes with suitable amounts of money."
Around 50 of the country's 390 FE colleges have residential facilities and researchers estimate residential fees will have to increase by an average 8 per cent.
Increased capital costs included refurbishing hostels, adapting showers and toilets, providing lockers and upgrading canteen or kitchen facilities.
These costs range from pound;14,000 to more than pound;1 million in each college.
The report says some colleges, particularly those which housed students under leasing arrangements, mistakenly believed they were not covered by the legislation.
The report recommends the LSC holds a central record of all colleges with residential accommodation for under-18s.