LONDON - Liberal Democrat leadership contender Chris Huhne is expected to pile more pressure on Gordon Brown on Monday when he urges police to investigate a planning decision involving the man at the centre of the Labour funding row.

Huhne will ask Durham detectives about the way official objections to a proposed business park involving property developer David Abrahams were overturned in the same year as he made a large donation to Labour.

Abrahams, who is at the centre of the scandal, has donated hundreds of thousands of pounds anonymously to the Labour Party, through third parties.

Huhne said in a statement on Monday: "Only if donations are openly declared can we be sure that donors have not benefited from government decisions and that there is no link between the two.

"That is why it is crucial that the Durham Constabulary investigate the lifting of the Highways Agency's objections to the planning permission sought by Mr Abrahams' company Durham Green Developments for a business park off the A1. Nearly 200,000 pounds was donated by Mr Abrahams through intermediaries in the same year."

Both the Liberal Democrats and Conservatives have been maintaining pressure on Brown during the weekend, demanding to know who knew about the illegal secret donations.

"I think what we've got to find out is who knew about this in the Labour Party ... I find it pretty incredible really that only one or two people knew about it," Conservative leader David Cameron told the BBC.

Acting Lib Dem leader Vince Cable said in a statement: "This sleazy affair is getting worse by the day. Who are the people that knew about these donations, and why didn't they do anything?"

Brown has acknowledged Labour accepted illegal donations and has ordered them to be returned.

Meanwhile, Wendy Alexander, leader of the Labour Party in Scotland and a close ally of Brown, came under pressure to resign on Sunday after she acknowledged receiving a donation of just under 1,000 pounds from a businessman based on the island of Jersey.

The businessman is not registered to vote in Britain and therefore barred from making political donations.