Conservative MP Hugo Swire has been filmed making jokes about people on benefits while auctioning off lots for more than £60,000.
Swire, a foreign office minister, played the role of auctioneer at the Black and White Ball, the Conservatives' glamorous fundraising gala.
Last month, BuzzFeed News obtained a list of everything the Conservatives auctioned at the party's fundraiser. For example, a trip on a private jet to Santorini sold for £220,000.
But Channel 4's Dispatches turns out to have been at the dinner, conducting an undercover investigation into party fundraising.
The full show, "How To Buy A Meeting With A Minister", was broadcast on Channel 4 on Monday night at 8pm.
An entrepreneur, Paul Wilmott, agreed to take part in the investigation. He joined each of the three main political parties, telling each that he was considering making a donation of up to £50,000.
Wilmott received an invitation to the Conservatives' Black and White Ball, held at the glamorous Grosvenor House hotel in Mayfair, by email. The email revealed that tickets for a seat on "premium tables" – where the table had a "premium position" and a cabinet minister would be seated – were on sale for £1,500.
Tickets for a seat on a "premier table" – joined by a mere minister – were on sale for £1,000 and standard tickets sold for £500.
This is what it looked like inside the venue.
And here's David Cameron at the event.
Swire was also recorded talking about the "good old days of MPs' expenses", joking that parliamentarians could have access to luxury vehicles.
The event was attended by the prime minister, cabinet ministers and hedge fund bosses, alongside other party donors.
Sir Alistair Graham, the former chairman of the committee for standards in public life, told Dispatches that he thought it was unlikely that detailed policy issues would be discussed at such dinners.
He also said: "I think it is about that feeling, if I make reasonable donations I'm in a special club who've got access to the leaders and that might be extremely useful as far as my business is concerned in the future.
"Ministers if they meet somebody formally in their offices are required to make that information public, now this jolly razzmatazz type affair they don't have to do that."
A Conservative spokesman told Dispatches: "The fact that donors to the Conservative party are invited to attend events with senior figures within the party is clearly and openly stated on our website.
"All donations to the Conservative party are properly and transparently declared to the Electoral Commission, published by them, and comply fully with Electoral Commission rules."
The Dispatches investigation had already led a Lib Dem peer to resign the party whip over allegations that he had breached fundraising rules.
Wilmott also met with Lib Dem business secretary Vince Cable and Labour's Chris Leslie, the shadow chief treasury treasury secretary, to discuss the introduction of a financial transaction tax that would have benefited a business he said he was going to set up.
Last week, in a separate investigation, The Daily Telegraph triggered the resignation of a high-profile Lib Dem parliamentary candidate after he accepted a potentially illegal donation from an undercover reporter posing as an Indian businessman. The reporter was also invited to meet chief treasury secretary Danny Alexander and party leader Nick Clegg.