Larry Flanagan, general secretary of the EIS teaching union, has written to Education Secretary Michael Russell highlighting the concerns. In the letter, Mr Flanagan calls on Mr Russell to ensure enough money is available to implement the recommendations of the Wood Commission.
The commission called for colleges to work more closely with schools and employers to develop broader skills amongst learners as well as calling for improvements to modern apprenticeships.
However, it comes at a time when colleges have seen their teaching budgets slashed and numbers of learners declining.
Mr Flanagan told the minister that a real terms cut of £56 million had been inflicted on the sector since 2010/11 (-6.2%) with funding for the next two years standing still in cash terms.
"In short, will the Scottish Government commit to providing the necessary resources to ensure the successful implementation of the Wood Commission's report and recommendations?" Mr Flanagan writes.
However, a spokesman for the Scottish Government highlighted a recent report by international development agency the OECD which praised some of the Scottish Government's efforts to reform the sector along regional lines. He said: "As the OECD has noted only this month, Scotland already has considerable strengths in vocational education, on which the interim report of the Commission for Developing Scotland's Young Workforce has outlined a blueprint for the future."