Further education union leaders forecast an "autumn of discontent" for colleges this week after support staff threatened to join lecturers in strikes over pay.
An increased offer from employers of 2.3 per cent was rejected on Tuesday both by Unison, representing 25,000 support staff in further education, and by lecturers' union Natfhe, which has 44,000 college members who staged a two-day strike last month.
After the meeting of the National Joint Forum for further education pay and conditions, Unison leaders said they would be recommending to their members that they turn down the offer and consider industrial action.
Natfhe leaders claimed that Unison's decision took employers'
representatives by surprise, and predicted it would mean joint strike action during Labour Party Conference week in September unless the offer was improved. The union leaders are due to meet next Friday to consider their next steps.
Unison said an additional offer from employers of a flat-rate £400 increase for staff on the lowest salary scales would affect only a minority of members, while a 2.3 per cent rise would be worth "next to nothing" for those on very low rates of pay.
Christina McAnea, Unison's senior national education officer, said: "For someone on salary point 12, this would be worth £256 per year, not enough to make a significant difference to their take-home pay."
The Association of Colleges, representing employers, said the offer was a "final offer" based on what colleges said they could afford on current funding levels.
Ivor Lewis, the AoC's director of employment policy, said employers were still committed to lobbying the government for extra funding to meet the unions' demands for pay increases to bring their members' salaries in line with those of school teachers.
He said it would prove difficult for the government to introduce proposals for reorganisation in further education, which could mean greater collaboration between colleges and schools, without such a change.
"We cannot have a situation where you have teachers and lecturers working side by side on different pay and conditions," he said.
Paul Mackney, Natfhe's general secretary, said there had been "too much pass-the-parcel" between the AoC, the Learning and Skills Council and the government over the question of pay and conditions for further education staff.
"In the end, it is the government that has the maximum power to make the necessary changes. Our members are very disappointed with its performance so far," he said.