More students were "forced" to work during term time "just so they can survive university", the TUC and the National Union of Students have warned.
Bar work is a popular choice among students
The number of full-time students with jobs rose by 54% in the last 10 years to 630,718, they claimed.
TUC general secretary Brendan Barber said those from poorer backgrounds were more likely to work and this had a "damaging impact upon their studies".
Higher Education Minister Bill Rammell said student jobs were "nothing new".
University tuition fees were rising to a maximum of £3,000 a year for students from England and Northern Ireland this autumn.
Some critics feared this would put people off applying for courses.
The TUC/NUS report - All Work and Low Pay - says 55% of young people from managerial and professional backgrounds work.
The figure rises to 61% for those with manual work backgrounds.
The report added that student employment was concentrated in the retail and hospitality sectors, with around 40% working in shops and 21% in bars, hotels and restaurants.
TUC General Secretary Brendan Barber said: "More and more students are being forced to look for paid work not only because they need the cash to survive each term at university, but also because they want to avoid running up massive debts by the time they graduate.
"This is especially the case among young people from poorer backgrounds who can't rely on regular financial support from their parents.
"Of course, working gives young people valuable experience which may help them secure that all-important first job and they are less likely to have money worries."
NUS president Gemma Tumelty said students needed to "become more empowered around their rights to decent pay and working conditions".
But Mr Rammell said: "There is nothing new in students taking term - time jobs.
"Many graduate employers want evidence that students have work experience.
"So long as the hours are not excessive, part time jobs can be beneficial."
He added: "It's indisputable that a degree is financially worthwhile.
"The graduate premium remains strong and three quarters of graduates feel that debt has not limited their choices following graduation."
The TUC/NUS figures were based on the government's Labour Force Survey.