The result at a time of rising numbers would be larger classes in both primary and secondary schools, Mr Fatchett said, and pointed out that one primary child in four is already taught in a class of more than 30 pupils.
Baroness Blatch, Minister of State for Education, admitted that posts could be lost but said there were positive reasons for this.
Surplus places were being eliminated and school duties reorganised to make more efficient use of teachers. 'Now that schools have their own delegated budgets it is to be expected that staff commitments will more closely match teaching demands. There is also evidence of schools employing more non-teaching staff so that teachers are to a greater extent recruited only for genuine teaching duties,' Lady Blatch added.
A survey by Labour of 15 typical education authorities showed that 10 were planning to make reductions and if this was extended to the 108 authorities in England some 4,420 posts in schools would be lost, Mr Fatchett said.
The number of teaching posts in England and Wales fell by 4,500 between 1990 and 1991, according to figures agreed between education authorities and the Department for Education. 'This snapshot is a warning of what we can expect over the next few years. Just as the number of secondary pupils begins to rise again, teaching posts are being cut,' he said.
'Large classes are back in the primary sector. With these losses of teaching posts, secondary schools will also be experiencing larger classes. This is simply no way to improve standards.'
Local authorities are blaming the Government for failing to fund the latest 7.5 per cent teachers' pay award in full and say they received pounds 300m less than they needed for the higher salaries.
Schools are now responsible for their own budgets based on pupil numbers, but many are finding that the funding formula meets only average salaries and does not cover more experienced staff.
Most posts will be lost through early retirement, or not filling vacancies. But for the first time teaching unions face the prospect of compulsory redundancies.