Unions have warned that staff are ready to take industrial action if colleges try to reduce salaries or increase hours as part of a national reorganisation.
The Educational Institute of Scotland (EIS) hit out as new colleges across the country - created by a raft of mergers - begin the process of harmonising conditions of service.
Staff at Edinburgh College are already out on strike over controversial changes to the hours they could be expected to work.
Larry Flanagan, general secretary of the EIS, said the action in the capital could be replicated across Scotland if colleges began a "race to the bottom" on pay.
In future, colleges will negotiate pay on a Scotland-wide basis following a return to national bargaining by the Scottish Government.
However, under the previous system colleges negotiated salaries with unions at individual institutions, which led to considerable differences for staff doing the same job in different parts of the country.
Mr Flanagan said: "The merger process could become a battleground for the further education sector if colleges try and remove hard won improvements to terms and conditions.
"Staff are clear that they are not going to allow discussions around harmonisation to result in colleges paying lower salaries or making staff work longer hours.
"With the significant variations in pay, conditions and contractual hours that have emerged as a result of the previous system, all colleges must start to consider how their own contracts compare to the best across the sector as we move towards a return to national bargaining for all further education staff."
A report by the Scottish Funding Council, which regulates public funding of colleges, found lecturers are paid between £31,000 and £37,000 in different parts of the country.
Promoted lecturers receive salaries between £35,000 and £43,000, while curriculum managers are paid between £35,000 and £47,000.
The disparities for heads of faculties are even greater, with some earning £36,000 and others receiving up to £70,000.
Another sticking point is the number of hours academic staff are expected to teach, rather than prepare lessons or mark work. In some colleges lecturers have just 21 hours' class contact time while in others staff are expected to teach for 28 hours.
The number of holidays staff are allowed to take also varies significantly, with some allowed 55 days and others getting as many as 65 days. The number of hours in a working week varies from 32.5 to 36.
John Henderson, chief executive of Colleges Scotland, said harmonisation would be complicated.
He said: "Harmonisation of salaries and conditions of service is ongoing at those colleges that have merged. This is a matter for each college to address.
"The college sector's merger programme has been complex, involving many hundreds of staff. Each college has its own strategy and timeline for harmonisation."
A Scottish Government spokesman said: "Staff pay and conditions are matters for colleges to determine. It is important that any disruption to students' learning is minimised and that both sides in any dispute work constructively towards a speedy resolution." The return to national collective bargaining - which is the system used by UK universities - was the result of a review of further education governance in Scotland conducted by Professor Russel Griggs in 2012.
In its response to the Griggs Review the Scottish Government enshrined the changes in the Post 16 Education (Scotland) Act of 2013, with Michael Russell, the Education Secretary, saying at the time: "I have long made clear my commitment to national pay bargaining in our colleges."
Staff at Edinburgh College are in dispute over a number of changes to their contracts including the requirement to work longer hours if covering for absent staff. However, the college says the offer is an improvement on what staff were expected to work in the three former colleges that merged.