The Conservatives have launched a fresh attack on the government over the school funding crisis.

During prime minister's questions, Iain Duncan Smith challenged Tony Blair on teacher redundancies.

"Perhaps he can tell us how many teachers are facing redundancy right now?" he asked.

The prime minister told MPs that there would be "around about 500 net redundancies", echoing Charles Clarke's estimate that the figure would not be significantly higher than in previous years

"We are looking carefully however at each of those and seeing where the local education authority or the department can help," Blair said.

"But I would point out to him that there are around about 25,000 more teachers in place now than there were when we came to office."

Duncan Smith said that the figures were misleading as they represented only the "third of the schools that have actually declared their position so far".

"And the estimates show at least 800 teachers are facing the sack directly as a result of the funding crisis," he alleged.

"And when the education secretary said that 'the overall level of redundancies will be of the same order as in past years', will the prime minister confirm that he was simply not telling the truth?

"The reality is the figures for redundancies are that three times as many this year will face the sack than last year."

Blair defended the statistics, but recognised that difficulties had been caused this year by one-off factors such as changes in national insurance and pensions contributions.

But he insisted that more money was going into schools, in contrast to Conservative commitments which he claimed would involve a 20 per cent cut in spending.

"Of course it is true that there are certain schools in certain parts of the country that have faced real funding problems, partly as a result of increasing costs, partly as a result of the changing formula," he said.

"However overall the position is as I have described, which is a very large increase in school funding."

"It is a small minority of schools that have been affected seriously...we are looking with their local education authorities and indeed the schools themselves at what we can do to help."

Returning to domestic issues after several sessions dominated by Europe and Iraq, the prime minister highlighted achievements in education.

"As opposed to the situation we inherited in 1997 we don't just have 25,000 more teachers, we have 80,000 more support staff, we have the best primary results we have ever had, the best GCSE results and A Level results and the largest ever capital programme," he proclaimed.

"Now it is true that as a result of the pressures on costs, not least the one-off payment on pensions, there have been real difficulties for some schools.

"But I simply say the answer to that cannot be his policy of opposing the extra investment in schools and imposing a 20 per cent cut across the board.

"And perhaps he can tell us how such a policy could possibly help any of the schools in financial difficulty."