Conservative Party co-treasurer Peter Cruddas yesterday resigned after secretly filmed footage showed him apparently offering access to the prime minister for a donation of £250,000 a year.
He made the claim to Sunday Times reporters posing as potential donors.
He said £250,000 gave "premier league" access, including dinner with David Cameron and possibly the chance to influence government policy.
Cameron said the claim was "completely unacceptable".
In the footage, Cruddas is heard initially saying that it was not possible to buy access to the prime minister.
But he then goes on to discuss what access different size donations would get.
He spoke about the Leader's Group, a club where for an annual donation of £50,000 donors are invited to join Cameron and other senior figures from the Conservative Party at dinners, post-Prime Minister's Questions lunches, drinks receptions, election result events and important campaign launches.