Universities around the country were accused of being heavy-handed after thousands of students were threatened with sanctions over failure to pay tuition fees. Many have already been excluded.
Ben Monks, national secretary of the National Union of Students, said:
"They are making a very bad system worse."
At the University of Liverpool, 5,500 students were sent letters warning them that if they did not pay their tuition fees, they would not be allowed to graduate or register for the next stage of their course.
Eric Bradshaw, assistant director of finance, said: "There are a lot of students that owe us money."
More than 600 students at Coventry University have been excluded from using academic facilities after failing to pay tuition fees. They will be allowed to sit exams, but their scripts will not be marked unless they pay up.
A spokeswoman said: "We have not taken this action lightly. It is not our preferred method of working, but we have tried everything."
Luton University has sent letters to 206 students who have not paid tuition fees or accommodation bills. Students will be prevented from taking exams - due to start on June 4 - if they have not made arrangement to pay their debts, which in some cases are expected to be met by the Student Loans Company.
The University of Central England has threatened to exclude 203 students whose fees are 90 days overdue. The university estimates it is owed about £100,000.
Peter Knight, UCE vice-chancellor, said: "If students convince us that they are going to pay shortly, we will take that into account. What we cannot afford to do is to take no action."
Sheffield Hallam University estimates that it will have a student debt of £1 million in the year ending July 31. It had sent more than 1,000 letters threatening exclusion by the end of April.