Under the agreement, struck between Scottish Education Secretary Mike Russell, local authority employers and teaching unions, supply teachers are paid a reduced daily rate of £78 for their first five consecutive days in a placement before the regular rate of £145 kicks in.

Its aim was to help councils fund other teaching priorities, such as keeping down primary class sizes and employing newly qualified teachers. But critics say councils are cutting placements to below five days and that teachers are leaving the supply lists.

The figures lend some support to these claims. They show that 84% of councils last year failed to meet all requests from schools for short-term cover, while 52% faced problems meeting longer-term supply needs. In the worst cases, four-fifths of day-to-day cover requests and almost a quarter of long-term ones went unmet.

Hugh Henry, Labour’s education spokesman, likened the pay cut to 1930s practices. ‘It is clear this penny-pinching deal from the Scottish National Party is having a devastating impact on the education of Scotland’s young people,’ he said.

‘It is not fair to pupils who are facing a succession of different faces, and it’s not fair to teachers who worked hard for their qualification and deserve a fair day’s pay for a fair day’s work.

‘I fear this rotten deal is leading to an exodus of some of our most experienced teachers. I urge the SNP government to provide our local authorities with adequate resources to scrap this unfair and unjust system now before this shortage turns into a crisis.’

The Scottish Government says the position is being kept under review, and that the raw figures overlook the numbers of supply teachers moving into permanent posts. Russell admitted to MSPs earlier this month that the issue ‘continues to cause concern’ and agreed to look at council areas where shortages were emerging.

Labour’s figures, secured under Freedom of Information legislation, do suggest that the picture is patchy. One local authority reports having lost 275 supply teachers from its books in the past year, while another records an increase of 229.

They also show savings so far to be relatively modest. Twenty of the 32 authorities detailed projected savings in the current year, and these totalled less than £3.24m.