Only 14 per cent of teachers and school and college leaders think that degree class indicates how good a teacher someone will be, a survey has found.
The poll also revealed that only 44 per cent believed primary teachers needed at least a 2:2 subject degree to do their job.
However, 62 per cent of the 662 state and independent sector respondents believed secondary teachers needed at least a lower second.
The findings come as the Government presses forward with plans to restrict funding for PCGEs to candidates with a 2:2 or higher.
The ATL, which conducted the poll, released the findings on the eve of its annual conference next week, where issues surrounding a major shake-up of teacher training are expected to take centre stage.
A key resolution asks the union to call on the Government to drop its plans to restrict funding to those with good degrees.
However, it also disagrees with plans to allow unqualified teachers to work in free schools, and wants the Government to retain rules which mean they are only employed as a last resort.
Executive member Ralph Surman will tell the conference that plans to restrict teaching to those with the best degrees will limit the number of graduates available in key subjects.
Citing a report from the University of Buckingham, he will highlight the fact more than a quarter of students training to teach physics in 200809 failed to get a 2:2 degree from a British university.
The primary deputy head will also attack plans to ramp up "on the job" training through schemes such as Teach First.
He will say: "To divorce education theory from practical training runs a serious risk of impoverishing teaching, with the consequent impact on pupils' learning.
"Trainee teachers can be given a range of techniques to follow, whether in teaching reading or in managing behaviour or in motivating pupils within their chosen subject. But they can only gain limited experience from their own practice."
Pisa guru says Gove is wrong on degrees, page 18
25% - Proportion of physics trainees without a 2:2.