A trade union official has called for a pause in plans to shut the Grangemouth refinery after casting doubts on claims made by the owner about its financial position.

A senior figure at Petroineos, the joint venture that operates the plant, claimed last week that it was “not commercially viable” and reaffirmed that it is losing £385,000 a day.

That put it on track for a £150m loss this year and the company plans to shut the facility next summer with 400 jobs likely to be affected.

Derek Thomson, Unite Scotland’s regional secretary, told a committee of MSPs that its research found the site was “a relatively profitable and financially healthy operation”.

He said its future as a repurposed facility could be secured if the two governments in Edinburgh and London took a stake in it.

Unite says it has produced a detailed plan which shows how Grangemouth could be initially converted into a Sustainable Aviation Fuel facility, before further developing into a full bio-fuels outlet.

Regarding the company’s figures, Mr Thomson said it was important not to view a single year in isolation and that it had been blighted by issues with the plant’s hydrocracker – a unit which produces jet fuel, diesel and liquefied petroleum gas.

He told the Economy and Fair Work Committee: “Unite’s position is that Petroineos has given a distorted picture of its finances.

“We do not share the narrative that it is a loss-making site and where it has made losses, not necessarily net losses, it’s down to a number of factors.”

Between 2014 and 2022 the refinery made a £49m net profit, if 2020 was excluded, he said, describing this as an “anomaly” year.

“The net loss is primarily due to a re-evaluation of assets; this one-off huge net loss distorts the overall picture between 2014 and 2022.”

He added: “The bulk of this so-called record net loss has come from the value under the plant and machinery section, which between 2019 and 2020 apparently lost 80% of its value and in 2021 accounts is worth less than 10% of its value.”

Committee members expressed concern that the “transition” to a green future was going too fast. Willie Coffey asked what would happen to the 54 million barrels a year that Grangemouth will be handling next summer.

Mr Thomson said another refinery in the UK is expected to take on the work, raising more questions about why it was not possible for it to remain at Grangemouth.

Referring to plans to turn the plant into a producer of biofuels, he said: “There is evidence to pause and evaluate a repurposing of Grangemouth.”

MSPs heard there were ongoing discussions involving the company and the two governments, through Project Willow, but Iain Hardie, Petroineos’s head of legal and external affairs, told the committee last week that ministers in both governments had come to the same conclusion about the plant’s viability.

In London, the Scotland Secretary Ian Murray, faced MPs on the Scottish Affairs Committee where he conceded that time was running out to save Grangemouth, while insisting “the site has a really bright future.”

Back in Holyrood, Green MSP Lorna Slater asked Mr Thomson what further help was required. “Does transition mean governments investing more?” she asked.

He replied: “There has been talk about nationalisation… we are looking for a transitional period with the Scottish and UK governments taking a stake. Let’s look a the costs and what needs to be spent.”

A spokesman for Petroineos said: “We have shared detailed operational and financial information with both Scottish and UK governments at various points over a number of years.

“This summer, we provided the incoming UK government with the latest financial information and gave them additional time to carefully consider the facts and any potential intervention.

“We have never received an offer of state intervention or financial support to extend the life of the refinery.”

A letter from Unite general secretary Sharon Graham to UK Energy Secretary Ed Miliband this week called for an independent review into the refinery’s finances.