David Cameron is under increasing pressure to reveal whether the Conservative Party's millionaire backers have been enjoying private dinners in Downing Street where they can lobby for changes to government policy.
Labour will try to force a minister to come to the Commons today to explain why the Tory co-treasurer, Peter Cruddas, was recorded boasting of the access a donor could buy for £250,000. Mr Cruddas resigned as soon as the scandal broke, and his remarks were disowned by senior Tories, who dismissed him as a newcomer to politics who did not understand the system and was making promises he would never have been allowed to fulfil. Mr Cameron told the BBC: "What happened is completely unacceptable. This is not the way that we raise money in the Conservative Party. It shouldn't have happened. It's quite right that Peter Cruddas has resigned. I will make sure there is a proper party inquiry to make sure this can't happen again."
But Labour politicians refused to accept that Mr Cruddas, who has himself given hundreds of thousands of pounds to the Tories, was genuinely ignorant about the relationship between political influence and party donations.
Mr Cruddas, the founder of an online trading company, was recorded by undercover journalists from the Sunday Times promising that a £250,000 donation would be rewarded by dinners with David Cameron and the Chancellor, George Osborne. He claimed that some donors had dined privately in 10 Downing Street with David and Samantha Cameron, and told the journalists that issues raised by "premier league" donors would be passed on to "the policy committee". It is assumed he was referring to the No 10 Policy Unit.
The Labour leader, Ed Miliband, claimed that the remarks raised issues too serious to be handled by an internal Tory party investigation. "There needs to be a proper independent investigation" he said.
The former Liberal Democrat leader, Sir Menzies Campbell, said yesterday that the Cruddas affair had strengthened the case for the state funding of political parties.
However, other leading Liberal Democrats have shied away from asking for greater taxpayer subsidies during a recession.