An independent oil company says that more than ten billion barrels of North Sea oil could remain untapped.
Paul Blakely, who works with 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.
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.