Colin Campbell, who retired at the last election as an SNP list MSP for the West of Scotland, has been investigating cases of heads who felt the action of teachers at their school led to them losing their jobs.
Mr Campbell said some heads "had been let down by their employers, vilified by elements of their staffs, conspired against, professionally humiliated, driven from their posts at huge personal and financial cost and their plight publicised in the press".
The former head of Westwood Secondary in Glasgow was persuaded to take up the cause of "bullied heads" and subsequently wrote to The TES Scotland asking for others to contact him in confidence.
Mr Campbell claims the close network of people in a small country like Scotland who cross the divide between unions, council officials and politicians can be responsible for unwarranted accusations. "Destroying a new headteacher in such a context is relatively easy, especially if the staff's line of communication into the local authority is longer established than the new headteacher's," Mr Campbell told The TES Scotland.
"The depute head and the senior management team will help the headteacher win round the difficult members of staff, but if one or some of them are counted among those hostile to the headteacher, the headteacher can be in real difficulty."
Mr Campbell acknowledges that incidents can be subject to varying interpretations. "To take a teacher aside and quietly suggest improvements to their work can be construed as informal professional development - or the teacher can claim harassment.
"To discipline someone legitimately, and have to do it several times, can be represented as vindictiveness on the part of the headteacher. It does not take much imagination to realise that a member of a strong social group so threatened can quickly find other alleged instances of harassment and start to build an informal case against the headteacher which, when the time is right, becomes a formal case for presentation to a union."
Mr Campbell criticises the unions, and the Educational Institute of Scotland in particular, for favouring teacher members above headteacher members in any dispute. The EIS protocol on bullying and harassment in the workplace suggests that it should assist both members where one raises a complaint against the other - but only where the member being complained against is not acting in a management capacity. Its guidance states that it is up to the employer to come to their aid.
Enquiries of the headteachers' organisations suggested that only the secondary heads' association had the financial clout to represent its members.
A series of parliamentary questions by Mr Campbell revealed that the Scottish Executive had no idea of the extent of the problem and thought it was essentially a matter for education authorities.
Mr Campbell says the Scottish Negotiating Committee for Teachers (SNCT), which is to monitor a new disciplinary framework, should take steps "to eradicate the procedural eccentricities that have made some school managers victims of weak local authority management, expedient rather than balanced decisions, undue influence and lack of transparency".