BLOOD donors who are O Rh negative (O-) and B Rh negative (B-) are being asked to come forward now to give blood.

Wimbledon mania and the arrival of summer have affected the numbers of people coming forward to donate. Across all blood groups, donations fell by 11 per cent during the last two weeks, when compared to the Wimbledon fortnight in 2012.

The fall was even more steep on Sunday. As excitement rose and the sunny outdoors beckoned, donations across all blood groups were 31 per cent down on the same Sunday last year.

Jon Latham, assistant director for marketing at NHS Blood and Transplant, said: “Summer finally arrived, temperatures and hopes rose during Wimbledon and blood donations fell.

“Stocks of blood for vulnerable blood groups - O Rh negative and B Rh negative - are lower than we would like them to be and I’m asking blood donors with those two groups, in particular, to walk in and donate now.

“By doing so you can help us replenish vital stocks and ensure that we can continue to meet the needs of patients.”

NHS Blood and Transplant, the organisation responsible for collecting, testing and delivering blood to hospitals in England and North Wales, has revealed that over the past two weeks O- donations were 11 per cent down on last year and B- donations were down 12 per cent on last year.

With the weather expected to be fair for at least another week, NHS Blood and Transplant is asking all donors with appointments to please keep them and those B- and O- donors who are eligible to donate to book an appointment or to walk into their nearest session to give blood now.

Donors with blood group O- are typically known as the “universal donor” as their blood can be given to patients with a different blood group. That can prove vital in an emergency situation when there mightmay not be time for an immediate blood grouping test to be carried out.

About seven per cent of the population have that blood group.

Donors with the blood group B- are more often found in Black and Minority Ethnic (BME) communities. Only two per cent of the population has that blood group and those donors are particularly needed as there is an increase in usage.

First-time donors should be aged between 17 and 65, weigh at least 50 kg (7 stone 12lbs) and in general good health.

There is no upper age limit for donors who have donated in the past two years. For more information or to book an appointment visit blood.co.uk or contact 0300 123 23 23.