Hourly paid lecturers from Scotland are making the daily commute to universities south of the border because pay rates are often more than double in England.
Experienced academics can earn up to £35 an hour at English universities, compared with as little as £16 an hour in Scotland.
Some lecturers are venturing as far south as Sheffield, a journey of three and a half hours each way from Edinburgh or Glasgow.
Earnings in Scotland are lower due to the tradition of paying hourly lecturers a rate equivalent to a demonstrator, rather than a rate equivalent to a full-time lecturer.
Demonstrator rates vary from £10 an hour to, more typically, £22 an hour. However, this higher rate includes payment for preparation, marking, administration and holiday pay, making the remuneration for an hour's teaching in effect as low as £16.
Even with the price of a train fare, Scotland-based academics can earn more by making the journey south.
The University and College Union in Scotland is campaigning against what it calls the "blight of casualisation" of university labour, and it has condemned the hourly paid rates in Scotland as "a scandal".
Terry Brotherstone, the president of UCU Scotland, said: "Hourly paid staff in Scotland have been included in the new pay framework and hence should be paid pro rata for their role. It is a scandal that hourly paid lectures are not being treated similarly to full-time colleagues and are not receiving the rate for the job."
The wide variations in hourly rates also apply in England. There is a national agreement on rates for the newer post-92 institutions, but no such agreement exists for older institutions. So pay rates at the older universities in England vary as much as at Scottish ones, but by comparison post-92 universities in Scotland pay the lower rates.
Rates in England vary from £19.59 an hour for inexperienced staff up to £35.70 for lecturers with more than four years' experience. At universities such as the University of Bristol the hourly rates range from £12 for a demonstrator to £68.
One Scottish hourly paid lecturer, who did not want to be named for fear she would not have her contract renewed, said: "You take extra hours to make up the money, but you end up working more than a full member of staff for terrible money."
Mr Brotherstone, an historian at the University of Aberdeen, said the problem was indicative of the broader issue of casualisation in higher education. He said that nearly half of the UK's academic and academic-related staff are on fixed-term contracts, a figure that rises to 85 per cent for research-only staff and 59 per cent of teaching staff on hourly paid contracts.
"Job insecurity blights our higher education system, bringing with it inefficiency, inequality and personal stress. The abuse of these groups remains one of UK higher education's biggest scandals.
"Hourly paid part-time staff are the most casual group in the sector. They are employed and paid by the hour, usually on termly or nine-month contracts. They suffer double casualisation by being both part time and fixed term."
Eva Hall (not her real name) from Edinburgh has eight years' lecturing experience in sociology. She returned to academia three years ago after spending a year looking after her daughter.
"I prepared and taught lectures, took tutorials and carried out administration, including moderation, as well as marking huge first-year classes for the typical rate in Scotland of £22 per hour of teaching, which includes holiday pay.
"I taught ten hours a week, which meant that, after tax, I received about £720 a month. I was paid only for each teaching week of the term, which was 20 weeks a year. Some of my (mostly male) colleagues who were full time taught six hours a week with no research duties, and their take-home pay was over £3,500 a month, every month.
"Then I found out that I could earn more than double in England. By paying a £6 single train fare and travelling 90 minutes, I now earn £35 an hour and get paid half an hour's rate for each essay I mark - and I often get preparation time on top."
Another lecturer who asked to remain anonymous said: "I travel twice a week to England to lecture in French, and I double my earnings. I do my marking on the train, so it's not dead time. A few English universities pay the low rate, whereas many Scottish universities pay the low rate. In a job I love and that took me nine years to qualify to do, to earn £15 or £16 an hour is laughable. It benefits no one - students, staff, parents, education sector, society - apart from the university's management.
"We are the invisible workers below the line of sight of unions, colleagues and management. Whatever annual pay increase is negotiated, it doesn't make a difference to most hourly paid lecturers, since the rates in Scotland haven't gone up for ten years.
"In England, however, the rate does increase, although in practice there are no annual increments on the spinal point. Also, most hourly paid workers I know in England and Scotland are women."