More than two thirds of lecturers are working an average of at least 11 hours of unpaid overtime every week, according to a new survey.
The poll of over 1,000 university and college lecturers, released exclusively to The Times Higher by lecturers' union Natfhe on the eve of its annual conference this week, found that the strain of excessive workloads was damaging to staff health and to the student experience.
"The goodwill of these dedicated professionals is propping up our universities and colleges but it is taking its toll on them in a way that no job should," said Paul Mackney, general secretary of Natfhe.
"It is very worrying that the majority feel that their workload affects their interaction with students. The situation is not tenable in the long term."
The poll, carried out online by Natfhe in conjunction with the Teacher Support Network charity, received responses from 1,138 lecturers.
It found that 69 per cent (778) of lecturers said they worked an average of 11 unpaid hours a week. Of those, nearly half (300) worked more than 12 extra hours a week to keep on top of their workload.
Some 94 per cent said an excessive workload had affected their personal lives, while 87 per cent said it had damaged their health.
The vast majority - 87 per cent - Jsaid the quality of support they could offer to students, and their students' learning experience, was damaged as a result of their workload.
Natfhe said employers were failing to monitor workloads to ensure staff work within the European Union's safe weekly limit of 48 hours.
Jocelyn Prudence, chief executive of the Universities and Colleges Employers' Association, said: "We would certainly support the development of a healthy work-life balance and we would not want to encourage a long-hours culture.
"However, it is very difficult to comment on a self-reporting survey that combines further and higher education. Without separating out the two sectors, it is impossible to know what the scale of the problem might, or might not, be in higher education."
The survey results follow the publication of a separate report from Natfhe earlier this week which found that about half of all teaching staff in higher education are now employed on hourly contracts. They are delivering well over half the teaching in some universities, the report found.
The report by Colin Bryson, of Nottingham Business School, found that hourly paid staff are undervalued and underpaid and that overreliance on them is damaging the quality of teaching.
Ms Prudence said she had not seen the Bryson report.
But she said: "In general, there are often good reasons why hourly paid staff are on that type of contract, such as enabling institutions to employ staff whose professional experience is current - practising architects, lawyers, engineers, artists and designers, for example.
"These people bring huge benefits to students and hourly paid contracts offer them the flexibility they need."
Both reports came as it emerged that Mr Mackney was due to make low workplace morale a key element of his annual address to the union's annual conference, to be held in Eastbourne during the bank holiday weekend.
Mr Mackney is due to lament a "macho" management culture and criticise an obsession with targets, saying: "Some of the things that really count cannot be counted".
He will say: "Macho management style is a major cause of poor morale.
Further and higher education must resist a target-driven compulsion to overmanage and coerce.
"Government should realise that a culture of punishing targets can be totally counterproductive. The 'floggings will continue till morale improves' strategy never works."