It fears that life-saving stocks will run low as regular givers find their time taken up with extra shopping, holidays and winter illness.

A lull in blood-giving is not unusual over the Christmas period. The service predicts that this year will be no exception.

Spokeswoman Liz Reynolds said: "The start of the new year coincides with the start of a traditionally busy time for hospitals and the need for blood in waiting list surgery."

Royal College of Nursing Secretary Christine Hancock is to give the service a boost on 6 January by giving her own blood at the union's London headquarters.

Ms Reynolds said: "We are delighted that the RCN is demonstrating its commitment to the need for blood. Nurses can save lives in more ways than one."

Ms Hancock said: "I hope by giving blood and encouraging staff here at the RCN to become regular donors, we can help top up current stocks and keep supplies healthy."