Petroineos said it expected the new distribution hub for finished fuels to open by early summer.

A spokesman said: “The process of safely transitioning the site from a refinery into an import terminal is under way and will continue over a number of months.

“Fully winding down and dismantling the refinery is anticipated to take around five years in total, so the new terminal business will operate in parallel with this process.”

Deputy First Minister Kate Forbes said it was “deeply regrettable” that Petroineos had issued redundancy letters to the workforce.

She said: “The Scottish government believes that refining at Grangemouth should continue, and a premature closure of the refinery is fundamentally short-sighted and detrimental to the transition to net zero.

“We stand ready to support everyone impacted and have announced dedicated skills support for those facing redundancy. And we will continue to do everything we can, within our limited powers, to secure a long term future for Grangemouth.

“However, the UK government has so far failed to live up to its commitments or offer any assurances about the future of Grangemouth and its workforce.”

She urged the UK government to bring forward investment to save jobs at the refinery.