Union leaders have voiced fears for the future of BP's Grangemouth oil and petrochemical complex.
About 500 people are employed in the division at Grangemouth
They told MPs that they were worried of a "Ravenscraig effect" as a result of the company's decision to sell off more than half its petrochemical business.
Unions said they feared that 20,000 jobs could go in central Scotland if the company decided to close the plant.
But members of the Scottish affairs committee were assured by BP that Grangemouth has a sustainable future.
BP announced the decision to sell off about 60% of its petrochemicals business in April.
The Olefins and Derivatives (O&D) division, which employs about 500 people at the plant, will be turned into a separate company which will either be sold or floated on the stock market next year.
The Transport and General Workers' Union reacted to the decision with shock.
The company said the move was the result of the global market and insisted that the sale would ensure the business remains competitive.
However, union leaders are concerned about the future of the Grangemouth complex, which employs 1,500 workers.
They told MPs on the Commons' Scottish affairs committee that they were concerned BP had already drawn up an exit strategy.
They expressed fears that splitting up the petrochemical and refinery businesses could spell the end for Grangemouth.
Unions said that, in the long term, closure might mean 20,000 job losses in central Scotland.
But their claims were dismissed as "alarmist" by BP executives.
Iain Conn, group managing director, told the committee that the plant had a good and sustainable future.
He also rubbished suggestions that the oil pipeline into Grangemouth might be under threat.
The O&D division makes products used in
plastic goods such as food and drink containers and automotive parts.
It employs more than 7,000 people across the world, including Germany and the US, and has about £3.64bn of the petrochemicals business' operating capital.