Allegations that Conservative Party donors were offered "cash for access" to Downing Street should be taken "more seriously" by David Cameron, Labour leader Ed Miliband has said.
The Prime Minister is facing demands for an independent inquiry after he confirmed he had hosted private meals at Downing Street and Chequers for wealthy individuals who had between them donated millions of pounds to the Conservative Party.
Mr Cameron has come under intense pressure after former Tory co-treasurer Peter Cruddas was caught on film telling undercover reporters that "premier league" gifts could secure meetings with ministers and influence policy.
Mr Miliband said the Government faces a "permanent stain" unless it agrees to an independent inquiry, as he joined Labour's London Mayor candidate Ken Livingston on the campaign trail in Bromley, Kent.
The Labour leader said: "We've seen Downing Street and Chequers have been used to entertain Conservative Party donors. What we need to know is the basis on which those discussions took place, the basis on which those dinners were arranged. That's why we need a proper independent inquiry.
"These are very serious allegations. I say to the Prime Minister that he must take them more seriously. He can't just have a Conservative Party inquiry.
"We've got to have an independent inquiry. It's the only thing that will remove the permanent stain that will otherwise be left on this Government and this Prime Minister."
Mr Miliband reiterated his belief that an independent probe should be conducted by the PM's official adviser on ministerial interests Sir Alex Allan.