Petrofac has bought a 20 per cent share in the Gateway gas storage scheme in the Irish Sea.
Gateway aims to eventually add almost 30 per cent to the nation's total gas storage capacity – which has been well below the level required in the UK.
Storage capacity is currently just five per cent of Britain's annual demand.
The project will see storage caverns in a natural salt structure below the seabed 15 miles off the coast of Barrow-in-Furness.
When completed in 2016, these will enable gas to be delivered, stored and then returned to the UK's national transmission system.
Gateway is led by Stag Energy directors George Grant and Andrew Stacey, who manage the project on behalf of shareholders which include private investors and financial institutions.
Petrofac managing director Rob Jewkes said: “We are entering the project at this stage to bring confidence to the investor group that execution and delivery objectives for the complete facilities can be met.”