Strike action at the Grangemouth oil refinery in Scotland may threaten fuel supplies to the whole of the UK, a union has claimed.

Unite, the UK’s largest union, said workers at Grangemouth have announced industrial action on Sunday 27th and Monday 28th April over plans to close the final salary scheme to new entrants and reduce provision for existing members.

But Grangemouth owner Ineos said it is “deeply concerned about the union’s cavalier approach to safety” at one of the country’s largest oil refineries.

Ineos claims Unite told the company it has ten days to remove all oil and gas from the plant and make the site safe – a physical impossibility, according to the company.

Tom Crotty, Grangemouth chief executive, said: “I have written to Tony Woodley, Unite’s joint general secretary, expressing our concerns. Ineos has always prioritised site safety, and I’m deeply concerned that the Union is putting other issues ahead of safety.”

The UK’s entire oil and petrol supply depends on the Grangemouth site staying at full production.

Unite claims a two-day strike at the plant will shut the North Sea and effectively stop production at the plant for up to a month. This will have an immediate impact on all fuel supplies, including aviation fuel, across the whole of the UK.

Ineos said shutting down the plant would have an affect on fuel supplies, but could not predict the extent of the disruption.

Unite joint national officer for the petrochemicals industry, Phil McNulty, said: “We are outraged by the company’s plans to close the Ineos workers final salary pension scheme when it has taken £40 million from the scheme and slashed its own contributions.

“Industrial action is never desirable but this is the only possible sanction against a company prepared to make such an audacious attack against our members,” Mr McNulty added.

Unite said 97 per cent of Unite members at the Grangemouth plant voted to strike over the pension dispute.