According to a survey by Natfhe, the lecturers' union, its members are doing an average of 11 hours extra a week, with much of their time at home spent on paperwork.
Natfhe says 69 per cent do nearly 12 unpaid hours a week, including marking and preparation. One of the 778 lecturers who responded to the survey said:
"Marking and preparation rule my home life. My six-year-old son complains about it. I miss out on family life. I have taught evening classes on my wedding anniversary and on my son's 18th birthday."
The survey was carried out with the Teacher Support Network. Patrick Nash, its chief executive, said: "Long hours have a devastating impact on lecturers' personal lives as well as their interaction with students."
Paul Mackney, Natfhe's general secretary, joined picketing strikers at Newcastle college on Tuesday in protest against long working hours. The college wants to increase the hours lecturers can work from 24 to 30.
Mr Mackney said: "In standing up for their workload, lecturers are defending the long-term interests of their students as well as themselves.
"The college has the support of the entire union. We continue to urge the college to accept Natfhe's offer to enter guided talks through Acas (the Advisory, Conciliation and Arbitration Service)."
Newcastle college claimed its students were studying "without disruption" despite the strike.