Heads are now expecting to lose a further 100 posts. Janet Jones, the Labour leader, warned: "Class size will rise and many children will not get the quality of education they deserve."
A survey of 265 primary schools in Cambridgeshire conducted by Mark Slater, county secretary of the National Union of Teachers, revealed that only 24 did not have classes above NUT action levels. These levels are 24 children in a mixed-age class, 27 in reception and 30 in a standard class taught across one age group.
"It is really terrible," said Mr Slater, "and things are going to get worse in the coming year. It is a grotty future for Cambridgeshire schools."
The county wanted to increase its Government-imposed spending limit by Pounds 5.8 million to put an extra Pounds 5m into school budgets and Pounds 800, 000 into social services.
"The Government claims to have produced more cash for three priority areas Q schools, social services and the fire service," said Ms Jones.
"We also want to give these services priority, but passing on the cash increases suggested by the Government takes us Pounds 5.8m above our spending limit."
MPs were due to rubberstamp ministers' proposals to reject such a move after The TES went to press.
The Government claims that Cambridgeshire should spend Pounds 2,467 per pupil, compared with the shire average of Pounds 2,552, and Pounds 2,617 in Oxfordshire and Pounds 2,697 in Bedfordshire.
Peter Lee, the Liberal Democrat leader, said: "It's nonsense that schools just over the county boundary should get hundreds of pounds more for each pupil than Cambridgeshire does."
Oxfordshire also challenged the Government limit and county finance officials estimated they needed to spend an extra Pounds 7.4m. While the limit was set to remain at Pounds 332m, ministers appeared prepared to allow Oxfordshire to borrow an extra sum.
John Barnwood, the county's chief executive, said: "Extra money is very welcome and will ensure that Oxfordshire's key services, such as education and social services, face fewer cuts this year than we feared.
"But, while this announcement shows that the Government accepts that we are in genuine difficulty, in the longer term its proposal only adds to our problems by leaving us with significant yearly interest charges."
Last weekend, hundreds of parents, governors and teachers in Oxfordshire and Cambridgeshire demonstrated against education cuts.