As many as 5,000 people a year are dying from infections caught in hospitals, according to the National Audit Office. BBC News Online looks at three cases.
"Superbugs" are feared by patients
Linda Brown was left severely physically disabled after contracting an infection in hospital.
She was infected with Methicillin Resistant Staphyloccocus Aureus - MRSA - one of the so-called "super bugs" which are highly resistant to treatment.
Infection by MRSA bacteria is increasingly common in hospitals, and there have been cases of bugs which show resistance even to vancomycin, an antibiotic traditionally regarded as "the last line of defence".
A 12-fold increase has been seen in hospitals in the last decade.
Physical exertion is now a struggle for Mrs Brown, who settled her claim for compensation with the hospital.
The infection has left her with difficulty in walking.
She told the BBC: "If they had taken proper precautions or noticed that it was there earlier than they did, I am sure something could have been done."
While not dangerous, and often symptomless in more healthy patients, in the elderly, weak or immuno-suppressed, MRSA can cause fever and pneumonia.
A large proportion of the healthy population are thought to carry MRSA strains without ever feeling ill, and many hospitals screen new patients with blood tests before they come into contact with other, more vulnerable patients.
Roseann Millar went into the private King's Park Hospital in Stirling for a hysterectomy operation in 1992, which should have meant a hospital stay of just a few days.
But following the operation she contracted necrotising fasciitis, a bacterial infection known as the "flesh-eating bug", and spent five months in hospital undergoing five operations.
Mrs Millar, a qualified nurse, from Bonnybridge, Stirlingshire, has since had to give up work and cannot walk without the aid of an abdomen brace.
She told BBC News Online: "At first I felt flu-like, then I noticed what looked like bruising around the hysterectomy wound.
"I was extremely ill and I now have extensive scarring to my abdomen, groin and hip."
She did not pursue any legal claim against the hospital saying she was too ill after the incident.
And she added: "Anyone who works in that field as I did knows that hospital is the worst place to be for infections and cross infections."
Necritising fasciitis is a bacterial infection that can be life threatening in extreme cases. The bacteria destroys soft tissue and is often coupled with toxic shock syndrome.
The bacteria usually enters the body through an opening in the skin. It can also enter through weakened skin, such as a bruise or blister, or following a major trauma or surgery.
Paul Hind was struck down by MRSA as he recovered in hospital from a heart valve replacement operation at the Merseyside regional Cardiothoracic Centre.
He was taken to intensive care two days after the operation and died a fortnight later. A post mortem revealed he died of septicaemia and suffered abscesses to his heart and spleen.
An inquest in November last year returned a verdict of misadventure and his wife claimed the hospital was to blame.
But the inquest heard that it was more likely the bug had been contracted from a visitor to the 60-year-old's ward.
Dr John Gosney, the pathologist who carried out the post mortem on Mr Hind's body, said: "The surgery was entirely successful. It was a post-operative infection which probably started in the wound."