Nearly 11,000 patients have died during the past seven months because of a failure by NHS hospitals to prevent them developing blood clots, a report claims.

Guidelines introduced in April mean every patient at risk should be assessed for treatment to cut the toll of deep vein thrombosis, or DVT.

But only one in three trusts is taking action, according to the damning report from the All Party Parliamentary Thrombosis Group.

It estimates that the failure to implement the guidance has cost 10,700 lives from DVT in the past seven months - nearly three times the number of deaths from the MRSA superbug and C Difficile infections.

The death toll in a year is greater than that from breast cancer, Aids and traffic accidents combined.

DVT is caused by blood clots forming in the deep veins of the legs. If they travel to the lungs it may trigger a pulmonary embolism that can cause them to collapse, and heart failure.

The blood clots often form as a result of immobility during and after surgery. If part or all of the clot breaks off and lodges in the lung, 30 per cent of those affected will die without treatment.

A substantial number of patients are struck by a surgical DVT - whose medical name is Venous Thromboembolism, or VTE - after they have been discharged from hospital.

The report says it is a "public health emergency" yet preventive drugs given at the time of surgery cost just £1 a day, while compression stockings can help others.

Altogether, 99 per cent of 140 NHS Trusts surveyed in the report are fully aware of the guidelines, but only 32 per cent are taking steps to assess patients at risk.

These include patients in hospital for longer than four days with reduced mobility, severe heart failure, respiratory failure, acute infection, inflammatory illness or cancer.

John Smith, chairman of the parliamentary thrombosis group, said: "The stark realisation is that while nearly all hospitals are now aware of what best practice looks like, and the steps they should be taking on a daily basis to protect their patients, over two-thirds of NHS Trusts admit to not having in place a mandatory risk assessment for every hospital patient on admission.

"DVT causes more than 25,000 deaths each year. It is worrying

that some NHS Trusts are still failing to adhere to these guidelines, which could reduce deaths by over 40 per cent."

Campaigners say DVT causes 10 per cent of all hospital deaths.

Dr Beverley Hunt, medical director of Lifeblood: The Thrombosis Charity, said: "The total costs of managing DVT within the NHS are estimated to be £640million and it's deeply concerning that the simple step of risk-assessing patients is not being taken.

"Any unwell adult entering a hospital bed has a 17 per cent risk of DVT but this risk rises considerably if they are over 40, are having surgery or have a predisposing condition such as cancer."

In March 2005, a report from the Health Select Committee warned the NHS was systematically and dangerously underestimating the threat from bloodclotting.

It found preventive drugs were cheaply and easily available but not widely administered.

The MPs recommended every hospital in the UK should set up a thrombosis committee to coordinate efforts to tackle clotting and raise awareness among staff.

A "suspected cause" of inaction by hospitals is the lack of agreement between two sets of guidelines issued a week apart by the Chief Medical Officer and the National Institute for Health and Clinical Excellence, the report says.

Nice recommended surgical patients aged between 40 and 60 be given compression stockings to wear in hospital, and possibly inflatable "boots" during their operation to encourage blood flow to the legs.

Blood-thinning medication - but not aspirin - should be given to everyone having orthopaedic surgery and those at high risk of developing a VTE.

Mr Smith said: "It appears that this has worryingly led to confusion and consequently stagnation in implementing new measures."

But consultant haematologists quoted in the report put the problem down to funding, saying: "If we had the money it would all happen tomorrow."

A spokesman for the Department of Health said: "The Chief Medical Officer has published a report by the VTE expert group.

"The report set out recommendations aimed at preventing VTE in patients admitted to hospital.

"We now have an Implementation Working Group driving forward actions to make a VTE risk assessment of every patient on admission to hospital a reality.

"We are also working hard to raise awareness of VTE among clinicians and patients."