Ken Clarke, the general secretary of the Principals' Professional Council, said the short period of notice - often as a little a month - that hangs over new principals during their 10-month probation can lead to damaging insecurity.
He has also criticised "the lack of proper understanding" of a principal's job among managers of local learning and skills councils. "It's pretty threadbare," he said. "There's a major staff development issue to get a grip of."
His comments follow the suspension of Graham Hilton from his post at Halton college in November on the eve of an inspection and less than a year into his job.
An internal investigation is expected to conclude shortly. Peter Kent, chairman of the governors, has declined to comment, although the college says there is no "financial impropriety or any other matter which might require external involvement".
Mr Clarke criticised a lack of support for new principals and said that "proper mentoring would avoid almost all the problems they face at a vulnerable time. It's a lonely job. It's very useful to be able to speak confidentially to a fellow professional."
An appeal for mentors was launched by the council and the Centre for Excellence in Leadership last term. Forty-six principals have volunteered, far more than expected. Thirty are PPC members, all of whom are serving principals. Since November, 20 have been trained by CEL's head of coaching Shaun Lincoln and some have now started work.
Mr Clarke said new principals need a better deal early on if they are to cope with the complexity of the job. "It's early days and so far we've had little feedback, but we feel the training was spot-on."
Matching mentor with principal needs care, he said. "Confidentiality is key. We look outside the principal's region; you can't have someone close to home with the competition issues that raises. Nor can you have someone with whom the principal didn't hit it off in a previous position."
"There has been informal mentoring in the past but things have been very ad hoc in FE. Where there are problems during a probationary period, too many corporations lack the expertise to deal with them."
Lynne Sedgmore, CEL chief executive, says the initiative is going well.
"There is a real sense of altruism. Some volunteers have had a good experience of monitoring and say how much it helped. Others say 'If only I had had it'."
Ms Sedgmore regards herself as lucky, having been mentored throughout her career, beginning at Croydon college. "Croydon was always quite forward in organising it. People have always stepped forward to offer me help."