The Scottish Government has pledged it will “explore all options” to support ExxonMobil workers in Fife, after the energy giant announced it is to close its plant at Mossmorran.

But Scotland’s Deputy First Minister Kate Forbes said it was also “crucial” that Labour ministers at Westminster “consider what more they can do for the workers at the plant and take urgent action”.

She spoke out at Holyrood hours after ExxonMobil announced its ethylene manufacturing plant, which produces the base material for many plastics, is expected to close in February.

The move puts 179 workers directly employed at Mossmorran at risk, along with the jobs of 250 contractors – although there is the possibility of 50 staff transferring to the Fawley Petrochemical Complex almost 500 miles away in Hampshire.

In a statement, ExxonMobil said its Fife Ethylene Plant “has been a cornerstone of chemical production in the UK for 40 years”,

However, the firm added that the closure “reflects the challenges of operating in a policy environment that is accelerating the exit of vital industries, domestic manufacturing, and the high-value jobs they provide”.

ExxonMobil said: “We considered various options to continue production and tested the market for a potential buyer, but the UK’s current economic and policy environment combined with market conditions, high supply costs and plant efficiency do not create a competitive future for the site.”

Ms Forbes said she was “extremely disappointed” by the move.

Speaking at Holyrood, she said: “I wish to provide my assurance to the workforce that we will work with them and their representatives to explore all options to support them.”

She pledged the Scottish Government would now “engage constructively” with Fife Council and others to “consider all possible actions to  mitigate any impact on the local economy”.

Ms Forbes also promised to convene a taskforce “to urgently consider any actions the Scottish Government, with the limited economic powers we have, could take to mitigate the impact of this decision”.

With the planned closure coming after the oil refinery at Grangemouth was shut down in April this year, the Deputy First Minister also said work to find an alternative future for this site would be expanded to include Mossmorran.

But she said the UK Government must work with her to “secure a future for the site”.

Ms Forbes said: “ExxonMobil has been clear in its announcement today that the UK’s current economic and policy environment does not create a competitive future for its site.”

Stressing that the “levers for an industrial intervention” lie with Westminster, she added: “I believe it is crucial that UK ministers consider what more they can do for the workers at the plant and take urgent action – overdue action – to address the high cost of energy which is slowly crippling industry.”

Scottish Secretary Douglas Alexander, however, said that the closure decision was “ultimately a commercial one” for the company.

“This is an incredibly difficult time for the Mossmorran workers and their families,” Mr Alexander said.

“The UK Government has explored every reasonable avenue to support the site, but the closure decision is ultimately a commercial one for Exxon, a company which is facing significant global challenges.

“Our focus now must be on supporting the workforce in the months ahead.”

Sharon Graham, the general secretary of the trade union Unite, said it was “utterly disgraceful” that the company had decided to shutter the plant.

“ExxonMobil must withdraw the closure threat and enter into meaningful negotiations with all key players to ensure the future of the plant and jobs,” she demanded.

The union’s industrial officer, Bob MacGregor, added: “Today’s news is devastating for the workers at the plant and the local community as well as the industry as a whole. Unite will do everything it can to support our members through the next few weeks.

“ExxonMobil is one of the richest companies in the world. It cannot be allowed to walk away and leave an industrial wasteland in Fife.”

Robert Deavy, a senior organiser for trade union GMB, which represents contractors on the site, called for politicians to put together a “planned and measured” transition.

“This is more grim news for workers, their families and communities but exactly how much more bad news is needed before ministers protect jobs and our country’s energy security? How many dominoes have to fall?

“Our members do not need more politicians wringing their hands or making more speeches promising just transitions. There is nothing just about what is going on and there is no transition.

“We need politicians willing to finally stand up and demand an industrial strategy that protects the UK’s crucial oil and gas while actually delivering a planned and measured transition instead of the economic carnage unfolding day by day.”