Lobbyists from TikTok, Amazon and gambling and crypto companies paid £3,000 a head to sit with ministers as part of the Conservative party’s business day, where Rishi Sunak set out his pitch to stop big corporates being wooed by Labour.

Senior ministers including Michael Gove, the levelling up secretary; John Whittingdale, a media minister; Robert Jenrick, the immigration minister; and James Cartlidge, a defence procurement minister, hosted tables of guests who had paid for access to the “policy” discussions.

They also had lunch and dinner with ministers, and appearances were made by the prime minister and Jeremy Hunt, the chancellor, at the event on Monday. Because the meetings took place at the Tory party conference in Manchester, there were no civil servants present to take minutes and witness the discussions.

Sunak told those at the lunch event that Labour “tolerated” them but the Conservatives were the ones really on their side and believing in business.

He said Labour was embarking on a “prawn cocktail circuit 2.0” under Keir Starmer and jokingly compared the party to the famous dish, saying it had “no backbone” and came straight from the 1970s. He also said attendance at the day was up 20% on last year – when Liz Truss was prime minister and dealing with the fallout of the mini-budget.

Whittingdale was seated next to a lobbyist for TikTok at the policy roundtable, along with corporate affairs representatives for Amazon, TalkTalk and Flutter, the betting and gambling company that owns Paddy Power and Betfair.

Ministers are expected to report back to their departments if they find themselves discussing official business without a civil servant present, so accounts of the meetings may end up being passed back to Whitehall.

TikTok, which is owned by the Chinese company ByteDance, has been banned from the phones of government ministers and parliamentary devices over security concerns, including whether data could be accessible to the Chinese state. The company has always said it is independent and denied its data is accessible to authorities.

Business leaders and lobbyists could pick which minister they would like to sit with to discuss policy, and there were about 20 tables in the room for about eight to 10 people each. The event was partly a fundraiser for the party, with tickets at £3,300 a person, raising hundreds of thousands of pounds.

Sources said the event was sponsored by the British Private Equity & Venture Capital Association and Bloomberg, and that it was dominated by delegates from the financial services, private equity and asset management industries, with presence from crypto industry representatives as well.

They said ministers had been keen to prove the Conservatives had a good offer to business and focused on telling City figures not to listen to Labour, and tried to drum up support for Sunak’s forthcoming artificial intelligence summit in London.

Business sources said it was all about trying to get people to invest in the UK as well as pushing the life sciences and AI sectors.

Tom Brake, the director of the Unlock Democracy campaign for greater democracy in public life, said the policy roundtables were “nothing more than a tailor-made opportunity for companies to lobby an influential minister and the Tory party to boost its coffers”.

He added: “Discussions of this nature should be conducted with civil servants present to ensure appropriate levels of transparency and accountability.”

Business representatives said Labour would be holding a similar day at its conference in Manchester next week but that it was oversubscribed and some were frustrated at not getting on the list.

The conferences are big money-making ventures for political parties with businesses, thinktanks, charities and others all paying for their presence at the gathering, with exhibition space or fringe tents.

Companies paying to sponsor fringe events often get a place on a panel talking alongside government ministers, and the chance to put across their messages to decision-makers.

Every night at party conferences there are drinks parties sponsored by lobbying companies, big businesses, media groups and donors, where MPs and ministers enjoy free hospitality and rub shoulders with corporate and media delegates.

Separately, party donors pay about £500 for conference tickets, with members of the most elite donor groups getting access to the “blue room” for networking as well as a special prime minister’s reception.

The Conservatives and the companies that attended the Conservative business day have been approached for comment.