Young people holding out for a college place on healthcare, family care or engineering courses are among those facing long waits, a Scotland's Colleges survey has revealed.
Some 21,280 applications were recorded on waiting lists for full- and part-time courses across 36 colleges - half from 16- to 19-year-olds, the government's priority age group, who have been promised a guaranteed place in education, employment or training.
Applications from prospective students aged 25 or under accounted for 15,918 places on the waiting list and demand was highest for full-time courses, with almost 19,000 applications.
The areas with the longest waiting lists were healthcare, medicine, health and safety (2,340), family care, personal development, personal care and appearance (1,958), and engineering (1,254).
Scotland's Colleges chief executive John Henderson said the figures showed that "colleges are being forced to turn people away".
"The high proportion of 16- to 19-year-olds on waiting lists is of particular concern, as they are the priority group for the government at the moment, and already over 70 per cent of colleges' delivery is focused on this age group."
The figures come weeks after an Audit Scotland report revealed colleges have to accommodate a reduction in their core teaching budget of 24 per cent in real terms between 2011 and 2015.
And last month a letter to the Scottish Funding Council from education secretary Michael Russell confirmed more FE funding would be transferred to Skills Development Scotland next year.
It is expected this will support more courses in line with the new college learning programme - short courses made up of equal amounts of college learning and work experience.
Some in the sector caution that the waiting list figures may overstate the problem as applicants tend to apply for multiple courses, resulting in likely duplications. Missing out on their first choice of a course, some applicants would also have returned to school or found a job or alternative training opportunity, without being removed from the waiting list.
Education secretary Michael Russell last week dismissed the claims of long waiting lists at Scotland's colleges: "It is absolutely wrong to suggest that there are 21,000 people on a `waiting list' who have been denied a place in learning. Many will have found their way on to other courses, or are pursuing other choices."
He said that some colleges were continuing to advertise course vacancies, "meaning that waiting lists for some opportunities are not the way to accurately measure overall demand".
Liberal Democrat education spokesman Liam McArthur said Mr Russell "should be careful not to dismiss out of hand these alarming figures", adding: "While 21,280 applications on waiting lists do not necessarily translate into 21,280 students, it may well be the case that thousands of would-be students are now on waiting lists instead of in the classroom."
John Henderson said: "While it is possible that some individuals will be on waiting lists for more than one course, that cannot account for the high numbers colleges are experiencing."