Around half are taking part-time jobs to support themselves through their courses, compared to only a quarter five years ago, and one in three expects to continue working during their demanding block teaching practice. Also, a worrying 29 per cent of students say they have missed part of their course because they were working.
The research, by Professor John Howson of Education Data Surveys, illustrates the increasing burden falling on undergraduate trainees - "the group the Government forgot" - at a time when it is pouring incentives into postgraduate training.
The ATL, meeting in Torquay for its annual conference next week, is expected to call for fees to be waived during the final year of BEd courses, and for students to e paid a salary during their block teaching practice.
That would bring them more in line with postgraduate trainees who pay no fees and now receive a pound;6,000 training grant.
Peter Smith, the ATL's general secretary, said cost had become a "powerful obstacle" to people who wanted to train as a teacher - at a time when the Government was trying to encourage more young people from impoverished backgrounds into higher education.
Professor Howson said: "People doing sandwich degrees are normally paid during their industrial placement. If so many students have to work during their block training experience, they should be getting a training grant."
Costs connected directly to the courses - such as books, travel to teaching practice and suitable clothing - have risen to pound;44 in a typical week, up by 40 per cent since 1995. Students estimated that they spent just pound;18 a week on their social life.
Some seven out of 10 trainees said they were constantly in debt, compared with just over half in 1995.