The credit rating given to Statoil by America's Standard & Poor's agency has been lowered following a fresh assessment.
This downgrading puts the group in the AA– bracket, one step below the AA rating it previously enjoyed.
The most important reason for the change is that Statoil now applies a stricter definition of its recoverable oil and gas reserves. This has yielded a 30 per cent technical reduction in reserves.
And Standard & Poor's believes the group's financial profile and earnings should have been better if it was to maintain its rating.
"This assessment shows how important it is that we continue our present restructuring to boost profitability," says Jon Arnt Jacobsen, senior vice president for finance.
"At the same time, it's worth emphasising that the group still enjoys a very good credit rating."
Only a few companies achieve the highest rating given by Standard & Poor's, AAA. These include Shell.