Hundreds of thousands of Londoners with ‘super blood’ are being urged to donate ahead of the Olympics.

There are as many as 349,000 people in the capital with the blood group O and demand for it is expected to be at least 70 per cent higher than donations being made during the games

New statistics from NHS Blood and Transplant (NHSBT) have revealed a gap between demand and supply of blood type O- during national celebrations. They underline an urgent need for O- donors ahead of the Olympics.

All blood types are needed to build stocks in advance of an exceptionally busy summer, but there is a particular need for O-donors to prepare for the Olympics.

An estimated 1.2 million people and 15,000 athletes are expected to visit London as part of the Olympic Games, whose blood type may not be known, so should they need a transfusion O- blood is likely to be needed. The increased demand will be compounded by low numbers of donors coming forward.

Type O- blood, often called the universal blood type, can be transfused into any patient regardless of their blood type and is used in over a tenth of hospital procedures.

Although O- blood is in the highest demand it is also in very limited supply. Around 7 per cent of the national population have O- blood, an estimated 360,000 people in London and just 11,000 of these are registered donors. Their contributions are vital for treatments of other blood groups in emergency situations but also to treat others of their own blood type since they can only be transfused with O- blood.

Jon Latham, NHS Blood & Transplant spokesperson, said: “Without O- blood donors many live saving procedures could be delayed or made more risky for patients and of course we wouldn’t be able to give transfusions to people with O- at all since they can only take blood of their own type.

“We’re appealing to this elite group of donors to help us prepare for the unprecedented demand expected around the Olympics, to make sure our health services have the essential stocks they need.”