College lecturers are to go on strike on Thursday in a long-running dispute over pay and conditions.

The Educational Institute of Scotland (EIS) said members would walk out over the refusal of college management to honour a deal that was reached more than a year ago.

The agreement promised equal pay for lecturers in all colleges and national terms and conditions following years of pay inequity for lecturers doing the same jobs in different colleges, the EIS said.

The strike comes after a 96% vote in favour of the action in a recent ballot of Further Education Lecturers' Association (EIS-FELA) members.

More than 4,600 members are eligible to take part in the strike, which will affect about 20 institutions.

EIS general secretary Larry Flanagan said: "After more than a year of waiting and watching college managers talk down the agreement that they freely signed up to, Scotland's further education lecturers have simply had enough.

"All that lecturers are asking is for the deal that was agreed by both sides to be honoured.

"Sadly, rather than working to deliver their commitments, college management have spent the last 13 months attempting to rewrite history and airbrush this binding agreement while simultaneously denigrating the hard-working lecturing staff in their colleges."

Picket lines will be in place at all colleges across Scotland covered by the 2016 National Joint Negotiating Committee (NJNC) agreement.

The EIS said Thursday's walk-out is the first day in a continuing and escalating programme of strike action.

A further one-day action is planned for next Wednesday, with the strike then escalating to two days per week and then three days per week unless the deal is honoured.

A demonstration will also take place outside the Scottish Parliament at 1pm on Thursday.

EIS-FELA president John Kelly, a lecturer from Paisley, said: "Rather than wasting taxpayers' money on spin against the agreement, college management should instead focus on delivering that agreement as promised."

College staff walked out on strike for a day in March 2016 and had more than 30 days of action planned.

A revised offer from Colleges Scotland was accepted last year, with staff promised wage rises as well as work between colleges and the union to develop a more ''harmonised'' pay deal across the workforce.

A spokesman for the Colleges Scotland Employers' Association said: "It is hugely disappointing that the EIS is taking strike action that will affect college students at this critical time.

"Colleges across Scotland are doing everything they can to minimise the disruption to students, who are currently preparing for their exams and finishing coursework.

"The strike is completely unnecessary and inappropriate at a time when we are currently engaged in Acas talks with the EIS to try and resolve this dispute. Harmonisation of pay and conditions is a complex process that requires compromise, not strikes and disruption.

"We are, however, pleased that the EIS now recognises the agreement reached in March 2016 is a 'deal on pay and conditions', because that is the simple reality.

"We have already agreed to an average pay rise of 9% over the next two years, but the EIS is striking to also secure an increase to 66 days' holiday and a reduction in teaching class contact time to 21 hours.

"The employers have agreed to pay the £40,000 top salary, plus a generous package that would provide 56 days' holiday and 24 hours teaching class contact time, with the facility to timetable up to 26 hours in any eight-week period. That is a very good deal by any standards.

"The EIS claim that 'the funding is sitting in college bank accounts' for the March 2016 agreement, but that is factually wrong.

"The EIS should call an end to this unnecessary industrial action, get back round the negotiation table with employers, and allow students to get on with their studies."