Oil refinery staff returned to work today as union members prepared to re-enter negotiations after their 48-hour strike.

Emergency fuel supplies are being shipped into Scotland following the industrial action at Grangemouth, where staff are resisting proposed changes to their pensions.

The strike has hit fuel supplies and closed a major pipeline bringing North Sea oil to the UK Workers turned up for their shift at around 6am at the plant.

UK Business Secret-ary John Hutton was at the plant this morning and said: "There is a gap between the two sides that has to be bridged - only the two parties can reach an agreement. No-one can do that for them.

"But I hope there is now a mood to try and reach an agreement."

Mr Hutton was joined at the refinery by Scottish Finance Secretary John Swinney.

Emergency fuel supplies arrived in Scotland to ease the pressure on forecourts yesterday, with more due to be shipped in from Europe today. A fleet of between 500 and 600 tankers is also expected to move out of Grangemouth to replenish supplies at filling stations.

Some stations in Glasgow today had no fuel left, including ones on Switchback Road, Canniesburn, and Great Western Road, Anniesland.

But although the workers restarted this morning, the recriminations continued, with the owners of the refinery - which is the only one in Scotland - raising the stakes by threatening to shelve a £250million upgrade plan.

The plan, which involves redeveloping the refinery's G4 wing handling ethylene production, was due to see the creation of up to 650 jobs.

Owners Ineos said if the dispute was not settled the investment and jobs bonanza could be lost to Belgium or Germany.

Ineos owner, Jim Ratcliffe was at Grangemouth yesterday to see the impact of the dispute. He was booed and jeered by workers on the picket line.

The venture capitalist bought the refinery from previous owners BP in 2005, and it is believed workers blame him for the pensions dispute that brought work to a standstill. He wants to close the company's final salary scheme to future employees.

An Ineos spokesman said: "It will cost £200m to replace that plant. That money will not be made available if our full salary pension scheme continues. If you win the pension scheme but lose the jobs have you really won?"

However, the workers' union, Unite, said: "Keeping the pension scheme open would cost just £1.5m a year. It is not linked in any way to the £200m investment."