The NHS would struggle to cope in the event of a major terrorist attack, a report reveals.

The National Audit Office has warned many hospital and ambulance trusts in England do not have adequate plans to deal with a biological, chemical, radiological or nuclear attack.

The situation is particularly poor in London - a possible prime target - where a large scale incident "would challenge the NHS", the report's authors say.

Some plans were still out of date

NAO report

The report comes just days after Prime Minister Tony Blair warned Britons to be vigilant against the high risk of terrorist attack.

Sir Liam Donaldson, the government's chief medical officer, pledged to take action to address the short-comings.

Poster campaign

The Department of Health will launch a poster campaign next year to advise the public how to respond in the event of a chemical or biological attack.

Officials are also planning mock attacks to ensure the emergency services are fully prepared.

The report by the NAO - the government's spending watchdog - found at least one in four major hospitals and one in three ambulance services are "not well prepared" to deal with an attack involving chemical, biological or radioactive weapons.

Half have failed to put proper plans in place to treat victims of a nuclear incident.

In London, one in three major hospitals and the ambulance service are "not well prepared" to deal with a major attack.

Sir Liam said the government was taking action

In addition, one tenth of all hospitals and ambulance services have failed to plan properly for a major incident involving 500 or more casualties.

The report also reveals the NHS would be unable to guarantee the safety of staff who treated patients caught up in an attack.

One third of all hospitals and half of all ambulances do not have proper protective equipment or decontamination facilities.

The figures are based on information from hospitals and ambulance services. But the NAO report suggests the situation may be even worse since some trusts were found to have exaggerated their level of preparedness.

The authors said while planning had improved since the terror attacks on the United States "some plans were still out of date".

They added: "Readiness in respect of chemical, biological, radiological or nuclear incidents was unsatisfactory."

Government plans

Sir Liam said the government was working hard to ensure the NHS would be able to deal with such an emergency.

Appropriate drugs have been stockpiled and guidelines published.

New threats now face us

Edward Leigh, Public accounts committee

Sir Liam said the proposed poster campaign and mock attacks were an important part of the government's plans.

He said: "It will be alarming for people but it is important."

The poster campaign will include tips such as running away from poison gas or using handkerchiefs as improvised masks.

Dr Sue Atkinson, the public health director for London, told BBC News: "Clearly there's lots more that could be done, particularly with training."

She said staff often felt more confident after taking part in simulations and training, but "when push comes to shove, they do know what they're doing and they can do things".

Shadow Health Secretary Dr Liam Fox called for urgent government action.

"It is disgraceful that these shortcomings have not been dealt with properly."

Liberal Democrat spokesman Edward Davey said: "National planning for a major emergency is a shambles."

Edward Leigh, chairman of the influential Commons public accounts committee described the report findings as disturbing.

He added: "The NHS needs urgently to build on the improvements they have made in emergency planning since 11 September.

"New threats now face us and the public will want to be assured that everything possible has been done to prepare for them.