A union has warned of further disruption for Scotland's colleges after support staff rejected a revised pay offer in a long-running dispute.

Unison members who responded voted by 89% to 11% to reject the offer from Colleges Scotland made at Acas talks in late October and early November.

The union is calling for support staff, who include catering and cleaning workers, classroom assistants and technicians, to have fair pay and a parity of wage increase with their lecturing colleagues.

Support workers at 20 further education institutions walked out in September, causing disruption to students with cancelled classes and the closure of campuses at West College Scotland and New College Lanarkshire.

The revised offer presented to Unison at Acas is a 1.5% pay increase for all support staff earning £22,000 per year or more, meaning that someone on £22,000 would receive £230.

All support staff earning less that £22,000 have been offered £400, Unison said.

Lecturers went on strike for a day in March earlier this year which led to a £450 settlement for them.

Earlier this month, Unison suspended two days of strike action in an attempt to bring the employer back to the negotiating table.

The union's further education committee will meet on Wednesday to plan its next move.

John Gallacher, Unison Scotland's regional manager, said: "This is a seminal juncture for the national joint negotiating committee, the Scottish Government, the (Colleges Scotland) Employers' Association and the sector as a whole. We need to write off the 2016 pay round negotiations as lessons learned and move forward.

"Scotland's colleges are run by a team of people and to say that one group of staff is worth more than another is divisive and wrong. Our members are not asking for anything more than they deserve - fairness and parity with their colleagues."

Unison has written to Colleges Scotland Employers' Association and Scottish ministers to urge a fair negotiated settlement to the dispute.

Shirley Sephton, vice-chair of Unison Scotland's education committee, said: "This strike has always been about equality of pay and terms and conditions. The employers' last offer rewarded the high earners and not the lower-paid support staff - the majority of whom would receive no more than the previous offer.

"This latest pay offer would increase a principal's salary, earning more than £150,000, by £2,150 - nearly 10 times more than someone earning just over £22,000 who would receive £230. The ballot result reflects the anger and disappointment support staff feel at this unfair treatment by college bosses."

Shona Struthers, chief executive of the Colleges Scotland Employers' Association, said: "It is extremely disappointing that Unison members have voted to reject the latest pay offer.

"The employers have offered a good package which would have ensured that all staff across the sector were receiving at least 2.5% over two years, with those below £22,000 receiving an increase of £800. This offer exceeds public sector pay.

"We look forward to meeting with the trade unions to discuss how we now progress."