PRESSURE was mounting last night for an independent inquiry into claims that access to senior Cabinet ministers could be secured by making large donations to the Conservative Party.

Tory officials spent yesterday dismissing suggestions by fundraiser Peter Cruddas that anyone paying the party £250,000 could discuss issues with David Cameron and other ministers – including Foreign Secretary and Richmondshire MP William Hague. The Prime Minister said the suggestions of access in return for donations were “completely unacceptable” and “should not have happened”.

A party spokesman said last night that Mr Hague, who this weekend attended an EU summit to increase pressure on the Syrian regime, held the same stance as Mr Cameron.

He said: “No Conservative politican has or would consider any access as the result of a donation.

“All donations to the Conservative Party have to comply with the requirements of electoral law.

"These are strictly enforced by our compliance department.

"We will urgently investigate any evidence to the contrary.”

Mr Cameron himself insisted that was not the way the Conservative Party raised money and promised an internal inquiry to ensure it would not happen again.

But Labour called for a full independent inquiry and sleaze watchdog Sir Christopher Kelly urged the parties to come through on their commitments on the big donor culture.

Former foreign secretary, South Shields MP David Miliband, described the disclosures as “grotesque” and said they showed the Tories had not changed.

“The revelations go to the heart of the Tory Party claim that you can trust the Tory Party because they have got rid of their bad old ways – from what we know, they haven’t,” he said.

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.

“Given the seriousness of the allegations about how Government is conducted, it is not appropriate for the Conservative Party to investigate itself. We need a full, independent inquiry,” he wrote to Mr Cameron.

Sir Christopher, chairman of the independent Committee on Standards in Public Life, said: “It would be wrong to regard this as an isolated event.

“Events like it are inevitable as long as the main political parties are dependent for their existence on large donations from rich individuals or, in the case of the Labour Party, a small number of trade unions.

“The parties collectively need urgently to address the damage this does to confidence in the integrity of the political process.”

Mr Cruddas, who became the Tories’ principal treasurer only at the beginning of March, was s ecretly filmed claiming that things would open up for anyone willing to donate £250,000 a year.

Speaking to undercover reporters, he said: “It will be awesome for your business.”

He said that “premier league” donors could lobby Mr Cameron directly and their views would be fed into the Downing Street policy unit.

Major donors are invited to private dinners and other events with Mr Cameron, Chancellor George Osborne and Mr Hague, he said.

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.”

He promised a “proper party inquiry” and stressed that he had already addressed issues within the Conservative Party.

But Lib Dem Douglas Alexander, the Chief Secretary to the Treasury, said the three main parties would be making a renewed effort on funding reform within the next few weeks.