David Cameron will urge Tory peers in the House of Lords to torpedo MPs' attempts to exempt themselves from the Freedom of Information Act, but it emerged yesterday that Gordon Brown is already considering amendments to the controversial legislation.

The Chancellor, who will become Prime Minister on June 27, has signalled that the legislation could be amended to protect publication of private correspondence between MPs and their constituents while ensuring that details of MPs' expenses are made available to the public.

Speaking at a news conference in London, the Tory leader said the Bill in its current form, which was masterminded through the Commons by David MacLean, a former Tory chief whip, would not be supported by his colleagues in the upper House.

"We will act to stop the Bill in its current form in the House of Lords," he said.

Even without Mr Brown's say-so it is highly unlikely that Labour peers would support the legislation so a defeat is almost certain.