The warning comes as ministers prepare to announce the results of years of deliberation on reform of the system for calculating councils' education budgets.
Peter Downes, a past president of the Secondary Heads Association and a member of the Government working party on education funding, said the cash was needed to ensure that no schools lost out in the review.
A primary in Tower Hamlets, east London, gets pound;4,100 per pupil compared to pound;2,700 in Lincolnshire. A secondary in Lambeth, south London, gets pound;5,600 per pupil, as opposed to pound;3,000 in Rutland.
Radical changes to the system will be introduced next April. Mr Downes said the Government needed to commit pound;2bn in 2003-4, and a further pound;0.75 bn in each of the following years, to ensure there were no losers.
Alan Parker, president of the Society of Education Officers, who also sits on the group, said: "Not to fund these changes properly would create substantial losers, which would be political suicide."