The OU, one of the largest providers of new teachers, has pulled out of primary teacher training from next February. It says the Government's new national curriculum for trainees entails a massive overhaul of its course materials.
The loss of 300 primary teachers at such short notice could threaten the Government's plans to bring down class sizes - unless its recruitment quango, the Teacher Training Agency, can force other universities to shoulder the burden next September.
The OU, which claims to reach the parts forsaken by traditional institutions, has apologised to 300 candidates who were expecting to start the 18-month post-graduate course in the New Year. Its secondary courses are unaffected.
The decision is bad news for trainees who want to study part-time. The course, which started in 1994, has a good record of recruiting mature students from the inner cities as well as rural areas.
"There's a surprising lack of alternative part-time routes," said Sir John Daniels, the university's vice-chancellor. "Unfortunately there will be few other opportunities for some candidates."
The decision has left the TTA with a headache. It must redistribute the places on a temporary basis even though other universities are unlikely to welcome the upheaval.
The TTA said it is examining the position, but insisted that all places will be reallocated for next September.
Don Foster, the Liberal Democrats' education spokesman, said: "Some high-quality candidates who can only study part-time will be lost to the system. I have spoken to the students and who are devastated. Why wasn't the TTA aware this problem was brewing?"