'If you can find a big buyer, you can do the sale without affecting the market. China and Japan are the potential white knights, because their gold reserves are so small,' said Naqvi.

Fears that a sell-off could send the gold price plunging have provoked fury among US senators, 20 of whom last week wrote to the Treasury Secretary, John Snow, urging him to reject the plan, which the IMF had been asked to investigate following a summit meeting of G7 finance ministers in London earlier this month.

But Naqvi says a sale could aid gold prices if Brown could drum up rich, new customers. The Chinese government holds only 1 per cent of its vast reserves in gold, compared to a global average of around 10 per cent. 'The basic feeling is that they need to diversify out of dollars, and the full 3,000 tonnes of IMF reserves allows them a one-time opportunity to do that.'

The gold reserves plan is the first stage in Brown's year-long campaign to use Britain's chairmanship of the G7 club of rich nations to introduce a 'Marshall plan' for Africa.

Proceeds from a gold sale would be used to pay for complete cancellation of the debts, worth $6bn, owed to the IMF by poor countries. At current gold prices only 420 tonnes (about 14 per cent of the total) would need to be sold to achieve that. 'This stockpile of gold is no use to anyone, and it could be used to help some of the poorest countries in the world,' said a spokeswoman for Oxfam.

Without US backing, Britain will be unable to get the 85 per cent support it needs on the IMF's decision-making committee for the sell-off to go ahead. The alternative is to revalue the reserves - which are written into the Fund's accounts at only $9bn but are thought to be worth up to $44bn.

However, a straightforward sale is thought to be the Fund's preferred option.