The Conservatives are selling access to Theresa May and other ministers for more than £3,000 a head to corporate executives and lobbyists at their party conference this autumn.

The executives will pay for the chance to attend a lunch session with the prime minister and a dinner with the chancellor, as well as more intimate “round table” sessions with ministers relevant to their industry.

The practice of charging corporate executives for access to ministers emerged under David Cameron, with the “business day” originally priced at around £1,000 a head for a session with the former prime minister and chancellor.

A new corporate brochure for the Tory party conference shows the price for attending the business day and dinner has now surged to £3,150 per person for the chance to be in the presence of May and her new government ministers.

The prime minister is listed as giving a question and answer session over lunch, with pictures of past events showing ministers mingling on tables with businesspeople.

In separate sessions, three Treasury ministers will host a talk billed as “Treasury insights” and business ministers will host a “partnering with business” session.

The website advertising the event features a picture of May, along with the claim that business day “offers representatives from the business community the opportunity to engage in discussion with senior Conservative politicians”.

May’s decision to participate in the event hints that she is not intending to break from Cameron’s previous approach to lobbying, despite her claims to want to run a country for the many not the few and tackle “vested interests” in the corporate world.

Tamasin Cave of the Alliance for Lobbying Transparency and Spinwatch, said it was “very concerning and worrying” that May was planning to “continue with politics as normal under David Cameron”.

She said there is a “bonanza of Brexit lobbying” coming down the tracks for May to deal with at a time when the public has little faith that politicians will stand up to powerful corporate interests.

“People do not trust establishment politicians on this issue of lobbying. She has a big problem on her hands, which she does not seem to understand,” Cave said.

Asked about the event selling access to May and other ministers, a Conservative spokesman said: “This is an important opportunity to engage directly with businesses and to highlight how, as part of our plan to create an economy that works for everyone, we will continue to back business and enterprise.”

Labour also has a “business forum” founded at around the same time, charging around £899 for a ticket and giving access to unspecified “politicians and leading businesspeople”.

The Lib Dem corporate event has gone down in price since the party declined in influence and left government, with a ticket costing just £240 to attend compared with £800 for their business day and £350 for their business dinner in 2014.

May will face calls to clamp down on lobbying next week, when Lord Brooke, a Labour peer, tables a private member’s bill arguing for the replacement of the current ineffective lobbying register with a genuine register that records who people are lobbying, their client, the type of influence they are seeking and how much they are spending.

Unlock Democracy, a campaign group, said the bill would bring the UK into line with other institutions such as the US, EU and Scotland.

“It’s time for Theresa May to put clear blue water between her and Cameron. She can set the tone for her premiership by backing real lobbying transparency,” it said.