Grampian police are investigating a complaint by the College Lecturers' Association of the Educational Institute of Scotland and the Scottish Further and Higher Education Association.
Lecturers sent two letters to board members criticising college managers, the second via Royal Mail. The first failed to arrive and the second was delayed. The unions claim a criminal offence of theft may have been committed.
The original letter said a board member had a possible conflict of interest by running an employment agency that supplies mostly support staff to the college. Lecturers also expressed anxiety about job losses and the failure to offer a pay rise for the current session. Staff have since been offered 1.5 per cent in the form of a one-off payment that will not be added to their salary.
The 75 CLA and 20 SFHEA members have been warned the college wants a single union for all staff and an end to collective bargaining. Linda Wheeler, the CLA's branch convener and national vice-convener, said: "The goodwill that has existed on the staff side has gone, people are very demoralised and extremely undervalued."
Elsewhere, the fault line between employers and unions, caused by tightening budgets, is about to fracture at Motherwell College, one of the largest in the country with 16,000 students. The college faces a deficit of more than #163;500,000 for the second year running and is planning voluntary or compulsory redundancies.
Motherwell lecturers also face the coming year without a pay rise, an increased teaching commitment and larger classes. Staff are to ballot on industrial action and will be strengthened by a CLA rally in the town on April 19.
Joe Eyre, the union's president, told a national meeting last weekend: "There is going to be continuing strike action to stop management in its tracks. The branch is totally united." Mr Eyre accused college managers across the country of being "gangsters, screwing the jobs of professional workers".
The meeting was told that Motherwell staff fear between 10 and 20 compulsory redundancies. Richard Millham, the college's principal, said this week: "I do not know if there will be any but there may be some. I anticipate single figures if any at all. I am hopeful there will not be." Staff may be redeployed.
Mr Millham said the college occupied an important place in Lanarkshire. It was successful but had to face harsh financial realities. "We have plans in place to bring us back into surplus in a two-to-three year period," he said.
The CLA meeting, at the union's headquarters in Edinburgh also heard lecturers complain of deteriorating relations with management at Lauder, Fife and Jewel and Esk Valley colleges.
Staff at Lauder in Dunfermline are protesting over the introduction of a new "associate" lecturer grade which they claim cuts salaries and increases weekly teaching hours. A ballot on industrial action is expected shortly. The threat of compulsory redundancies at Fife and Jewel and Esk Valley is also alarming CLA members.