College students and staff have presented a petition signed by 60,000 people to Downing Street in a call over better funding.
The focus is switching to adults without basic skills and to teenagers
They want the government to protect adult education courses and to equalise funding between schools and colleges.
The government is focusing its funding on teenagers and adults without basic literacy and numeracy skills.
The college sector warns that hundreds of thousands of college places could be axed over the next few years.
The petition, to be handed in on 1 November, was launched by the Association of Colleges in March.
It is supported by a range of organisations, including Help the Aged, the National Federation of Women's Institutes, the RNID and some teaching and students unions.
Association of Colleges Chief Executive, Dr John Brennan, said: "This petition shows how strongly people feel about their local college and we would like to thank all those who have worked hard to make it so successful.
"These 60,000 signatures are compelling evidence that the government should think again about reducing learning opportunities for adults wanting to improve their career chances and personal development."
The organisation says colleges across the country face a cut of up to 200,000 adult learning places this year - with further cuts predicted for future years.
The colleges also complain that the 700,000 16 to 19-year-olds attending colleges are funded by an average £400 a year less than teenagers studying at school.
The government recently announced that adult learners would have to contribute more towards the cost of their courses, so more resources could be directed at 16 to 19-year-olds and to adult learners without basic skills.
The union Natfhe represents most lecturers at further education colleges.
The organisation's Barry Lovejoy said: "Thousands of Natfhe members working in further education signed this petition because every day they see the damaging effects of the unjust 13% funding gap between colleges and schools, and of the diminishing pot of public money for colleges' popular work with adults.
"We urge the government to take steps to prevent colleges from being irrecoverably damaged."
A spokesperson for the Department for Education and Skills said funding for further education had actually been increased by 48% in real terms since 1997.
But he acknowledged that there was a funding gap between school sixth forms and colleges, and said work was continuing to narrow that gap.
With regard to adult education, the spokesperson said:
"While total funding going into the learning and skills sector will increase over the next two years, there is a need to rebalance spending toward priority areas.
"This includes a shift toward longer and more expensive courses for adults seeking the skills they need for employability and further progression into learning."
Next year there will be 274,000 more places for adults learning basic skills to level 2 (GCSE level), but the overall number of publicly funded adult learning places would be reduced by an estimated 230,000, he said.