The cabinet minister in charge of negotiating a new US trade deal met with a series of rightwing American thinktanks to discuss deregulation and the benefits of “Reaganomics”, new documents have revealed.

Liz Truss, the international trade secretary, had a number of meetings with libertarian groups that have championed parts of Donald Trump’s deregulatory agenda and tax cuts.

New details of her three-day visit to Washington last September have been uncovered by Greenpeace’s investigative journalism team, Unearthed. Truss met senior representatives from the Heritage Foundation, a thinktank committed to shrinking the state and cutting environmental regulation, to discuss “regulatory reform”. Also at the meeting was the Competitive Enterprise Institute. Both groups were part of the “shadow trade talks” project, designed to advocate a wide-ranging US trade deal allowing the import of American goods currently banned in Britain.

One briefing note reveals that Truss was keen to hear “what we can learn from ‘Reaganomics’ on things like regulation and red tape”. Truss also planned to tell the Heritage Foundation that she is “committed to”, and “personally interested in”, exploring similar reforms in the UK. “Reaganomics” is shorthand for the policies of the former Republican US president Ronald Reagan, based on tax cuts and deregulation.

Truss has made no secret of her interest in cutting the size of the state. However, she is now in charge of Britain’s post-Brexit trade deals in a government committed to leaving the EU with no deal if necessary. Many fear a no-deal Brexit will pave the way for a weakening of UK food and environment protections. The US agricultural sector has insisted that any deal scraps restrictions on chlorinated chicken, hormone-treated beef, and pesticide usage currently circumscribed by the EU.

John Sauven, Greenpeace’s executive director, said: “There are widespread concerns that Brexit will be used to weaken our safeguards on food safety and animal welfare, opening the floodgates to products such as chlorinated chicken and hormone-treated beef. These concerns will only grow at the discovery that the minister in charge of forging a trade deal with the US flew to a libertarian boot camp run by Donald Trump’s buddies to be lectured about the supposed benefits of ditching regulations.

“Boris Johnson promised that a trade deal with the US would not jeopardise our food and animal welfare standards. People will be watching closely to see whether these words mean anything at all.”

Truss also met the chief economist of the American Legislative Exchange Council (ALEC), which involved a discussion of the success of Trump’s efforts to deregulate the US economy. ALEC has lobbied against action on climate change, with companies including Shell, BP and ExxonMobil quitting involvement in it as a result. Another document has revealed that an official from the Foreign Office wrote to another free-market thinktank, R Street Institute, on Truss’s behalf requesting a meeting to discuss “business deregulation”.

A government spokesperson said: “We are committed to negotiating an ambitious free-trade agreement with the US. Without exception, imports into the UK will meet our stringent food safety and animal welfare standards. That’s not going to change.”