Euan Blair attends the London Oratory School

Ten - which is funded by 85% of LEAs in England and Wales - said a total of 23 former GM schools received over �200,000 more than they would have done under the fair funding formula applied to other local education authority-maintained schools.

A further 72 schools received over �100,000 more than they would have done through the formula, the research indicated.

When it came to power in 1997, New Labour prevented any more schools from seeking GM status (where they opted out of local authority control) and promised to phase out the extra money given to existing ones by the previous Conservative government.

But Ten is angry that the government has announced it will no longer subsidise the transitional funding arrangements for these schools.

"This will leave LEAs to find the full amount - and because no end-date for the transitional arrangements has been set by Whitehall, other schools will continue to lose out," said the co-ordinator of Ten, Martin Rogers.

Mr Rogers said the total cost to LEAs last year would have been �32m but the government had met about half of it.

'Outrageous'

"It is bad enough that, after all these years, former GM-schools continue to receive substantial additional resources that are denied to their more needy neighbours," said Mr Rogers.

"That they should now once again do so at the direct expense of those neighbours is completely outrageous."

He urged the government to re-visit these arrangements urgently and draw them to a rapid and fixed conclusion.

A spokeswoman for the Department for Education said transitional funding would not continue indefinitely.

"Levels of transitional funding have fallen sharply this year and, as a result of high delegation and the effect of the local government funding settlement, this trend is likely to continue," she said.