Most supply teachers are earning less than £124 a day and some have been driven to using food banks, a survey by the NEU teaching union shows.
In the survey, which had responses from 1,450 members, 14 per cent of respondents said they earned less than £100 per day, while 44 per cent made £100-124.
Twenty-six per cent received £125-£149 and just 9 per cent more than £150. The rest said the pay varied by placement.
A daily rate of £100 would result in a supply teacher earning £4,000 less than a newly qualified teacher in a full-time post, the NEU said ahead of its supply teachers’ conference this weekend, where it is to launch a charter for supply teachers.
Seventy-eight per cent of respondents thought their pay was either lower or significantly lower than the rate for the pay point on which they were most recently employed.
Supply teachers 'underpaid and undervalued'
As a result of low pay, 56 per cent had taken on non-teaching work, while 17 per cent claimed benefits and 2 per cent had resorted to using food banks.
NEU joint general secretary Kevin Courtney said: "The situation for supply teachers is becoming ever more invidious, with experienced teachers not only underpaid but undervalued.
"With so many reporting that they need to claim benefits, or even turning to food banks, it seems incredible that such a situation can have grown amidst a retention and recruitment crisis across the profession as a whole.”
He said the root causes of the problem were “a collapse in traditional pathways to work…in parallel with an explosion in agencies, who, with their commission, are a further drain on schools' narrowing budgets".
"In turn, the workload facing permanently-placed teachers is driving many into supply. This is a downward spiral, damaging not just to teachers' wellbeing but the range of experience available to a school and the pupils they teach," he added.
The charter sets out the union's aspirations for its supply members, including a new system for supply teacher employment free of agencies and umbrella companies, and a guarantee that pay reflects both experience and the national pay arrangements for permanently placed teachers.