The Grangemouth refinery strike and militant attacks in Nigeria pushed the price of oil to a new high today, just shy of the $120 a barrel mark.

In early trading, a barrel of US light crude hit a record $119.93. It fell back slightly to $119.40 by 9am.

Traders said that the Grangemouth dispute had led to new fears of supply shortages. Workers at the refinery began a 48-hour strike yesterday, forcing BP to close its Forties Pipeline System – which delivers a third of the UK's North Sea oil to the mainland.

Neither side in the dispute over pensions has shown any sign of backing down. There were reports on Sunday that further "secret strikes" could be planned, which would also disrupt fuel supplies.

Militant attacks in Nigeria have also pushed the oil price higher. On Friday, Royal Dutch Shell was forced to cut production in the country after rebels attacked one of its major oil pipelines.

The price of a barrel of oil has risen by 25% since the start of the year, partly driven by the weakening dollar. Industry group Opec has resisted pressure to increase production, saying that the current high prices are caused by speculation rather than supply issues.

Britain's motorists are feeling the pain at the pumps where prices are also at record highs. The AA reported this month that petrol now costs an average of 109.2p a litre, with diesel now priced at 119.3p.