David Cameron is facing demands for an independent inquiry into explosive claims that access to the Prime Minister could be secured by making large donations to the Conservative Party.
The Prime Minister has been plunged into a damaging row over party funding after Tory treasurer Peter Cruddas urged reporters posing as wealth fund executives to give more than £250,000 in return for direct face time with senior ministers.
Mr Cruddas resigned within hours of his claims being exposed by The Sunday Times and denied that party donors could in fact improperly influence ministers.
Mr Cameron insisted that was "not the way" the Conservative Party raised money and promised an internal inquiry to ensure it would not happen again. Danny Alexander, the Prime Minister's Liberal Democrat Cabinet colleague, described the claims as "utterly disgraceful".
Labour called for a full independent inquiry into the "incredibly serious" allegations of cash for access.
It emerged later that the matter has been reported to police, with a Metropolitan Police spokesman saying an allegation had been made under the Political Parties, Elections and Referendums Act 2000 and was currently being assessed.
The row led to renewed calls for reform of party funding. Sleaze watchdog Sir Christopher Kelly warned that the incident could not be seen as "an isolated event" and urged the parties to come through on their commitments to the "big donor culture".
Mr Cruddas, who became the Tories' principal treasurer only at the beginning of March, was secretly filmed claiming that "things will open up" for anybody willing to donate £250,000 a year. Speaking to undercover reporters who were posing as wealth fund executives, he claimed: "It will be awesome for your business."
Mr Cameron said: "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."
Shadow minister Michael Dugher wrote to the Prime Minister demanding that he disclose which Tory donors had visited Downing Street, Chequers or Dorneywood since May 2010 and what policy representations they had made, particularly on the top rate of income tax that was cut in Wednesday's Budget.