Business secretary Kemi Badenoch said that there is “zero” chance of the UK securing a post-Brexit trade Deal with the US while Joe Biden remains in the White House.

The cabinet minister risked a diplomatic row with Britain’s closest ally by saying the Democrat president was too “close” to the unions to strike a free trade agreement (FTA).

It comes as a report claimed that Rishi Sunak and Mr Biden were in the early stages of a “foundational” UK-US agreement on trade aimed at being wrapped up before they both face re-election in 2024.

Appearing at a Tory conference fringe event hosted by The Spectator magazine, Ms Badnoch was asked about the possibility of a deal during the current administration.

“Under this administration – zero,” Ms Badenoch said. She said that the Biden White House has “very close links with unions”, who are opposed to free trade agreements.

Asked if a Trump-led White House could be more amenable, she did not directly answer the question. “An FTA is a tool. It is not the answer to everything. There are other things you can do. You don’t always have to wait for the FTA with the president or his administration.”

It comes as Politico first reported that negotiations on a “foundational” deal on trade were set to begin between the UK and the US this month.

Although it will not qualify as a formal FTA in the eyes of the World Trade Organisation, it is expected to cover controversial areas like labour rights, environment rules, supply chains and regulation of services.

It has been initially dubbed the US-UK Trade Partnership Forum (TPF) with the aim of making sure the two countries can “coordinate and cooperate on trade policy issues of mutual interest and to further deepen existing trade ties”.

UK government sources played down the significance of the potential “foundational” deal to The Independent, since it is not believed to be anything approaching the FTA promised in the Tory manifesto.

A spokesperson for Ms Badenoch’s Department for Business and Trade pointed to the ‘Atlantic Declaration’ struck in June. The declaration is a loose economic concord aimed at boosting collaboration on energy, artificial intelligence and other areas.

The spokesperson said: “The UK and US are rapidly expanding the work we do together across the full spectrum of our economic, technological, commercial and trade relations through the Atlantic Declaration. Discussions with the US on next steps under this first-of-its-kind agreement are ongoing.”

Ms Badenoch – believed to a leading contender to replace Mr Sunak if the Tories lose the election – has been showered in praised by the Tory faithful this week after striking a deal for Britain to join the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP).

The UK formally agreed to become the first European country to join a major Indo-Pacific trade bloc – hailed as “momentous” despite forecasts placing its value at just £1.8bn a year.

Reminded earlier this year that a “promise was made” by the Tories on a US trade deal, Ms Badenoch told the BBC: “That was an agreement with the previous president [Donald Trump]. You cannot force countries to join free trade agreements.”

The right-winger used her conference speech to attack Sir Keir Starmer over his support for Remain in the Brexit referendum. “The people who tell you that Brexit is the cause of every problem, do so because they think the answer to everything is the EU,” she said.

And Ms Badenoch told a fringe event: “Our political opponents are obsessed with viewing every problem as Brexit – relentlessly wanting to talk down our country.”