The newspaper revealed footage of now-resigned Tory co-treasurer Peter Cruddas telling potential Conservative Party donors that cash would provide “premier league access” to the Prime Minister, including dinner parties.

After initially saying no cash amount would buy access, he told reporters posing as wealthy investors from Lichtenstein,  "Two hundred grand to 250 is premier league… what you would get is, when we talk about your donations the first thing we want to do is get you at the Cameron/[George] Osborne dinners."

David Cameron called the revelations “unacceptable”, and Mr Cruddas has now resigned his post.

But a new row has now erupted over Mr Cameron’s refusal to disclose the names of those who have had private dinners at Number 10 (many of them are believed to be party donors) because the details are “private”. The Prime Minister has however promised a full investigation into any potential wrongdoing however.

Labour leader Ed Miliband called for the full disclosure of guests at Number 10, fearing the issue would get “swept under the carpet”.

He said, "We need to know what access was paid for, if access was paid for, and what contributions were made and the interaction between the prime minister, the chancellor and Conservative Party donors."

Cross-party discussion on reform to party funding is set to begin in the next few weeks.