An independent oil company says that more than 10 billion barrels of North Sea oil could remain untapped.
There is still plenty of oil at the bottom of the North Sea, says an expert
Paul Blakely, vice president of Talisman Energy, says that large energy corporations are no longer interested in extracting and selling the reserves.
The warning comes amid rising prices of crude oil and growing concern about the security of supplies, following attacks on oil compounds in Saudi Arabia.
This year prices have soared by 25% to levels not seen since the early 1980s.
The UK Offshore Operators Association has said there are plans to extract less than half the oil thought to be left in the North Sea.
Mr Blakely told BBC Five Live: "Reserves that might otherwise be produced may in fact be left in the ground so I think that is a concern for us.
"It may well be that many billions of barrels, possibly ten, possibly more, it's difficult to judge, may be left behind."
During the 1970s multinational companies invested millions of pounds developing the area.
Currently, they prefer to drill for oil in more common locations and industry experts say that exploration in the North Sea is at an all time low.
Insiders also say under-used assets have not been sold on to smaller companies keen to exploit them in new ways.
If methods are not discovered soon to get at the remainder of supplies in the North Sea, the infrastructure that brings it to the surface will be too old to use.
Geoff Runcie, chief executive of Aberdeen and Grampian Chamber of Commerce, said: "The debate is about can we foster the churn, can we foster people to release licences and let the new players, with their new business models, come forward and create a second wave of energy in the north sea."