Discussing the trip with the undercover reporter, Littlewood confirmed Carnuccio was raising money for the IEA. “We haven’t seen a cent of it yet – we quite often… we speculate to accumulate,” he said. “So with Oklahoma and [Carnuccio] and Tucker coming over we wanted to show what we thought was possible.

“It was almost like a trial run: the fact that we were able to get them in to see four members of the House of Lords, five MPs for lunch, Jacob Rees-Mogg and the European Research Group.”

An aide to Baker said: “Any suggestion – or implication of the same – that Mr Baker would attend meetings because ‘access’ to him was being sold is entirely false.”

She added: “On the occasion you refer to, Mr Baker met US Republicans in his political capacity to discuss trade relations between the two countries.”

Singham told the undercover Unearthed reporter that if the supposed US agribusiness funded his work, he would also be happy to “show them round” in the UK.

“[I]f they think there is something worth doing, then we’d agree that we would do something and they would fund and support our trade work in some way, and if it’s a donation of X to our trade team so that they, so we can do more work on the US-UK [free trade agreement] then absolutely, when they came over we’d show them round and, you know, decide on a body of work going forward.”

The IEA’s spokeswoman said: “[W]e have received no money to support our trade or Brexit work from any foreign business to date. Given our strict protocols we see no reason however why we should not.”

She described Unearthed’s evidence that the IEA is fundraising from agribusiness donors who stand to benefit from deregulation as “tendentious and unfair”. She added: “The prospective donors are businesses who stand to benefit from free and open trade in accordance with UK regulations which should be in line with sound science and democratic accountability. UK businesses and consumers will also benefit from this.”

The E Foundation issued a statement: “The conversations supported the E Foundation’s purpose to explore global business and research opportunities. The informal conversation enlightened us on possible mutually beneficial endeavours in the future between [the] United Kingdom and Oklahoma. Any suggestions the conversations were about something other than constructive business and research pursuits would be completely misguided.”

Intimate dinners

Littlewood also revealed the IEA hosts intimate dinners at its London headquarters at which leading politicians are matched with “five or six donors who have an interest in the area” and “two or three journalists”, although the meals are off the record. Donors can “get to know cabinet ministers on first name terms”, Littlewood said.

At the dinners, he said, “Everybody gets to know each other… it’s an opportunity for you to say, ‘Minister, I’m really keen to bend your ear about beef from the west coast of the USA… Can I send you a note about it? Can I speak to one of your policy advisors about it?’ All of these conversations are happening because we facilitate them.”

Littlewood said the IEA is not a lobbying organisation, describing the charity as a “great facilitator” for business to connect with senior politicians.

An IEA spokeswoman said there is “nothing untoward” about the IEA’s contact with senior politicians, adding: “We do not act in donors’ interests, except to the extent that they have an interest in pursuing free trade and free markets. We put people in touch where we feel there is a genuine interest on both sides.”

But Sir Alistair Graham, the former head of the committee on standards in public life, told Unearthed: “It is disturbing to see that such a respected think tank as the IEA are seeking donations for access to lobby ministers at private lunches or dinners.”

Charity rules

Fundraising from donors who stand to profit from the IEA’s policy recommendations may contradict assurances it gave to the Charity Commission. In 2016, after a complaint by former Charity Commission board member Andrew Purkis about its lack of transparency, the trustees told the regulator the “only sponsored research IEA accepts is from individuals or trusts who do not have a vested commercial interest in the topic under discussion.”

The IEA also assured the commission that “companies donate money to the IEA for their own reasons and the IEA’s role is to ensure that it is ‘blind’ to these reasons… and no company is able to guide IEA’s research conclusions.”

But Littlewood told Unearthed’s undercover reporter that the IEA is happy to solicit research funding from companies with commercial interests in the research subject they are planning to cover. “To give you an example,” he said, “we would take money from alcohol companies – we would go to alcohol companies and say we want to write about the cost of living being too high and actually alcohol consumption is not costing the National Health Service as much money as they often complain”.

There are also concerns that the IEA’s push for a Brexit that allows the UK to reduce regulations and sign a sweeping US-UK trade deal amounts to a political campaign.

As an educational charity, the IEA is able to accept tax-free donations but must abide by Charity Commission requirements to be politically impartial, balanced and neutral in how it presents information and stick to its charitable object of education.

In written guidance the charity commission notes that “Raising people’s awareness of an issue to build support for a campaign is not educating them about this issue as the aim is to gain their support.”