Image caption Officials say extra blood donations will be required next year

Blood stocks may be hit by 2012 events like the Olympics and Diamond Jubilee, according to the NHS body responsible for England and north Wales.

Extra bank holidays could lead to a drop in donations as most people give blood during the working week, said NHS Blood and Transplant.

It says hospitals will need about 2m pints (1.1m litres) of blood, plus an extra supply for Olympic visitors.

It called on the public to make blood donation a New Year's resolution.

Supplies of donated blood are needed by the NHS for people having surgery or giving birth and those with conditions such as cancer and sickle cell disease.

NHS Blood and Transplant said it was concerned the cluster of major events in 2012 could create a "perfect storm" and dramatically impact the number of blood donations coming in.

Assistant director for blood donation, Jon Latham, said: "Approximately two million units [470mls - just under a pint] of blood will be needed by hospitals throughout 2012, and the equivalent of 500 extra donations will be needed each week in the first six months to help us build blood stocks and cover extra potential need from Olympic visitors.

Blood donation The NHS needs 7,000 voluntary blood donations daily

First-time donors should be aged 17-65, weighing at least 50kg, and in good health

You can give blood three times a year

Source: NHS Blood and Transplant

"We're calling on the public to make regular blood donation a New Year's resolution.

"Whether you've never donated before or haven't done for a while, please book your appointment and help save lives in 2012."

Figures show that in 2011 thousands fewer people donated blood due to a crop of bank holidays around Easter and the Royal Wedding.

And in 2010, on the day of the football World Cup quarter final, and Andy Murray's Wimbledon semi-final, there was a 12% drop in donations compared with the previous year.

In 2012 there will be a cluster of events and bank holidays between April and August, including the Queen's Jubilee, Euro 2012, Olympic Games and Paralympic Games.