The Association of University Teachers is refusing to mark assessments and complete end-of-term student reports because of a dispute with managers over new pay deals.
It means that all undergraduate and postgraduate teacher-training students will be left without the necessary qualifications to begin working.
According to figures from the Teacher Training Agency, up to 25,000 students going into teaching could be affected.
As The TES went to press this week, the AUT's annual conference in Scarborough was debating whether to continue with industrial action.
Some prospective teachers have written to their institutions seeking assurances that the matter is resolved so that they can take up job offers for September.
They fear that their final teaching practice, which ends on June 15, will not receive written feedback or end-of-practice reports.
One letter, sent by student teachers at Goldsmiths college, in London, said: "These documents are necessary to complete our professional qualification, recommendation for Qualified Teacher Status and ultimately our registration with the General Teaching Council. We urge the college authorities to resolve this issue without delay."
Lecturers are angry at plans by university managers to introduce new contracts which could leave thousands of staff financially worse off.
Although lecturers have been offered average pay rises of more than 12 per cent, managers want to end national pay agreements and set up their own salary structures.
A spokesman for the AUT said: "Such a move would bring to an end the concept of equal pay for work of equal value. It would mean that, over a career lifetime, thousands of staff could end up much worse off."
Following talks held last week, university managers agreed to ensure that lecturers and support staff did not end up worse off under new individual pay arrangements and the talks are continuing.
The National Union of Students said it supported the AUT's action. A spokesman said: "We do not want to see students being taught by demotivated lecturers. It is important for students to get the most out of university.
"We are hopeful that, following negotiations between the two sides, the matter will be resolved quickly and that any backlog in assessment will be cleared."
The TTA said it hoped for a speedy resolution to the dispute.