Billiton, the metals group planning a pounds 5.1bn stock market flotation this month, said yesterday it had been given "assurances" by the the Treasury that it would be excused from a ruling announced in the Budget forcing companies to take a double taxation hit on dividends paid out of foreign earnings.

Mick Davis, finance director said the new measure would have been "very material" to the group's flotation plans, but that a personal meeting with the Paymaster General "entitles us to be confident that this will not affect us".

Mr Davis said he expected the exemption to be applied to other companies, suggesting the Government may do a U-turn on this hugely unpopular measure: "I'm sure its not a solution just for us, but a generic solution," said Mr Davis.

Should Billiton be singled out for exemption, it would leave Rio Tinto, Billitons's bigger rival, facing a double tax bill on the 70 per cent of its dividends paid out as a "foreign income dividend" from non-UK earnings.

The comments came as Billiton, which is being demerged from the South African mining group Gencor, published details of its pathfinder prospectus. Brian Gilbertson, chairman said the group would use the $1bn-$1.5bn raised to expand in a range of privatisations in South America, but said he could not be specific on spending plans.

"The best returns are from being ready and able when an opportunity presents itself." Mr Gilbertson denied suggestions that the board was too heavily represented by Gencor directors: "These are the people who have shown their ability to take risks."

Asked to compare the group against its only UK stock market comparator Rio Tinto, he said, "We will be much smaller. Growth comes more easily to a smaller company."