Ineos bosses have insisted they do not know exactly when controversial plans to close a “highly inefficient” oil refinery at Grangemouth will take place.

MSPs have heard that the facility’s transition to a fuel import terminal will continue until at least the spring of 2025.

The company which owns Scotland’s only refinery said the site is “highly inefficient” and macroeconomic conditions mean it cannot continue operating at a loss.

Read more: SNP ministers criticised for delayed Grangemouth just transition plan

Iain Hardie, head of external affairs at owners Petroineos, spoke to Holyrood’s Economy Committee on Wednesday.

The company is a joint venture between PetroChina and Ineos.

He confirmed that of the refinery’s 500 current jobs, only around 100 would be retained when it becomes an import terminal.

Other parts of the wider complex at Grangemouth – such as the Forties pipeline system which brings in North Sea oil and gas – will continue, he said.

Mr Hardie said: “We will operate through to at least 2025.”

He said the company’s announcement was for the start of the transition rather than the closure of the refinery, with Mr Hardie saying “we don’t know when this will be”.

Mr Hardie added that “we have made the announcement” but added that “we are at day one of the process".

Read more: SNP hopes to 'extend the potential life' of Grangemouth oil refinery

He added: "We have not made a decision as and when we will be closing the Grangemouth refinery.

"There is a recognition that the refinery will close. We wouldn't be putting in place these measures if we had line of sight to the refinery operating for the next 20 years.

"That's simply not the case. No one in the refining industry, within UK or Scottish Government, I think reasonably believes that."

Grangemouth is “one of the oldest (refineries) in Europe and highly inefficient”, he said.

Mr Hardie said domestic demand for fuels is falling away due to increased use of electric vehicles and hybrids.

Read more: Ineos accused of 'greenwashing' after Grangemouth carbon capture and storage plans revealed

The sharp increase in oil and gas prices due to the war in Ukraine has not changed the fundamental outlook for the facility, he said.

Over the last decade, the refinery had incurred losses of more than 1 billion US dollars (£800 million), the committee was told.

Committee convener Claire Baker expressed surprise at how quickly the closure had been announced, saying she and her fellow MSPs had visited the site earlier this year.

Ms Baker said: “From the outside, this doesn’t look like a just transition for Grangemouth.”

Labour MSP Colin Smyth warned that the staff “will be looking for other employment, presumably, because you can't give them any certainty beyond 2025”.

Wellbeing Economy Secretary Neil Gray spoke to the committee later on Wednesday morning.

He said a just transition plan for Grangemouth would be published by spring next year.

Mr Gray said the Scottish Government was in discussions with Petroineos over retaining as many jobs as possible.

He said the prospect of 400 roles being lost was an "assumption, not a definite".

The GMB trade union has said news of the plant’s closure is “deeply worrying”.