SHETLAND's North Sea oil plans have been dealt a blow after an oil giant cast doubt over the viability of a potential £6 billion project off its shores.

Chevron said yesterday that its Rosebank scheme, 80 miles west of the islands, was not currently economically attractive.

The announcement has raised doubts about the future of the field amid mounting fears over costs.

In a statement, the company said that the project could not currently justify "proceeding with an investment of this magnitude".

It added that it would require a floating vessel to ensure that oil was produced stored and then offloaded from the field, which lies in 3600ft of water.

Chevron believes the field has the potential for 240 million barrels of oil to be recovered.

Rosebank remained in the initial engineering phase, the company added, with a final investment decision planned for 2014.