Nurses have been told to shape up so they are fit enough to do their job and to set an example to patients, in new standards from their regulator.

Amid spiralling obesity levels, the watchdog’s new rules for the first time say that Britain’s 650,000 nurses and midwives have a “professional responsibility for adopting a healthy lifestyle”.

More than half of NHS staff are obese or overweight, contributing to a £5bn annual bill for the health service on conditions caused by obesity.

Nurses will be told they must “maintain a level of personal fitness and wellbeing required to meet people’s needs for mental and physical care,” amid concern that too many are too unfit to carry out physical tasks.

The standards, from the Nursing Midwifery Council, follow repeated efforts to encourage NHS staff to slim down.

In recent years, the head of the health service has attempted to tackle the problem by limiting the amount of unhealthy food on offer in hospital canteens and cafes, and financial rewards for trusts which run weightloss and fitness schemes.

Health officials are concerned that too many NHS staff are setting a bad example, while attempting to dole out advice to the public about how to improve their own health.