Sales of land at the Games site in east London could raise Ј1.8bn by 2022, Olympics minister Tessa Jowell said.

The money will be used to repay Ј675m, which will be diverted from lottery good causes from 2009, and Ј650m to the London Development Agency (LDA).

A further Ј410m has already been promised from the National Lottery.

Ms Jowell told the Culture, Media and Sport Committee: "The decision about when the land is sold will be on the basis of selling the land in the most favourable circumstances."

The LDA bill will be settled first to repay the money it spent buying the land at the Games site, but a proportion of all sales would go to the lottery fund with any profits shared in proportion to the contribution given.

"Everybody would want the lottery to get its money back as quickly as possible but these are decisions that have to be taken relative to the land values at the time," she said.

"At this stage, what I would not be prepared to do is to predict with any certainty that the land sales will exceed the Ј1.8bn we have predicted."

Critics said the estimates were "wishful thinking".

London Assembly's budget committee chairman, Brian Coleman, said: "Based on the 'prudent' estimates given to us today, lottery good causes might only receive a repayment of just Ј151m of the extra Ј675m they are being forced to contribute to the Games."

Sports school plan

The current budget of Ј9.325bn, triple the original, was only set 10 months ago. It includes a contingency fund of Ј2.747bn.

One plan for the Olympic stadium is for a school designed to "nurture sporting and related achievement" after the 2012 Games.

A panel including Cambridge County Council's retired chief executive, Ian Stewart, Sue Campbell, chief executive of UK Sport, and an education expert will advise ministers in June.

Schools Minister Jim Knight said: "The review will provide us with an expert assessment of the role which learning on the stadium site could play in time to inform the legacy plans we are now developing for the park."

The Ј496 million stadium in east London, once reduced from an 80,000-seat to a 25,000-seat arena after the Games, should firstly be a sports arena, Ms Jowell said.

Talks are continuing to find a football or rugby club as an anchor tenant.