Theresa May has held private talks with the Ineos founder Sir Jim Ratcliffe, Britain's richest man, about his blueprint for a new off-road vehicle amid growing scrutiny of his personal tax affairs.
Sky News has learnt that Sir Jim met the prime minister and Greg Clark, the business secretary, late last week to discuss the 4x4 project, which Ineos has said will be constructed either in the UK or in Continental Europe.
Sources said that Sir Jim had also raised concerns during the meeting about the Government's fracking policy, which he publicly criticised last week as laying a path for an "energy crisis" that would cause "irreparable damage" to the UK economy.
While private meetings between Mrs May and senior business figures are not unusual, the timing of the discussion has the potential to be embarrassing for her.
Last weekend, The Sunday Times reported that Sir Jim and two of his fellow Ineos shareholders had been working on a restructuring of the company to enable them to reduce their tax bills by huge sums of money - potentially running into billions of pounds.
The tax restructuring work is understood to have been underway since the middle of last year, well before it emerged in August that Sir Jim was relocating to Monaco.
While the tycoon, who was last year crowned Britain's wealthiest person, has publicly backed the Brexit deal promoted by Mrs May, his decision to move his personal domicile to the French principality has triggered criticism from, among others, members of the shadow cabinet.
Ineos has been examining for months whether to build its new off-roader at Bridgend in Wales, a site on Teesside or a number of locations in Europe.
The company had said it was aiming to reach a decision by the end of the year, although Brexit-related uncertainty may now lead to an announcement being delayed until after next month, according to insiders.
It was unclear whether Mrs May or Mr Clark offered any new financial incentives to Ineos to locate the project's manufacturing base in the UK during last week's meeting.
The chemicals giant is keen to secure Government support for the project, and received a letter from ministers including Mr Clark last November pledging "unrivalled corporate tax support".
However, any formal commitment to providing financial assistance will be particularly sensitive in the wake of a row about promises made to Nissan in 2016 to secure its commitment to build its X-Trail SUV in Sunderland.
Sky News revealed the Japanese car-maker's u-turn on that decision earlier this month, sparking anxiety about the industry's fortunes that intensified on Monday when Honda decided to close its Swindon factory in two years' time, with the loss of thousands of jobs.
A Number 10 spokesperson said: "The PM and the business secretary met with Jim Ratcliffe last week to discuss Ineos's latest project."
The official confirmed that the project which had been discussed was the off-roader, although she declined to respond to a question about whether the shale gas industry had also been on the agenda.
Ineos has been working on Projekt Grenadier - named after the London pub where the Ineos founder came up with the idea - for several years, having identified a gap in the market for a successor to the Land Rover Defender.
The company has said its ambition is to create "an uncompromising off-roader that stands for adventure and active driving, but also has the capability to be a work and utility machine".
Britain's largest private company, Ineos redomiciled to Switzerland following a row over its VAT liabilities, but returned to the UK in 2016.
Projekt Grenadier is being led by Dirk Heilmann, the chemicals group's former head of engineering and technology.
Ineos did not respond to several requests for comment about Sir Jim's meeting with Mrs May and Mr Clark.