The agency has cut the amount of money lost to fraud

Figures from the government's Counter Fraud and Security Management Service (CFSMS) shows patients defrauded the health service of more than �100m last year.

This typically involved people who should pay prescription charges claiming they are entitled to medicines free of charge.

Officials said the amount of money lost to fraud has fallen sharply in recent years and insisted "huge strides" were being made in tackling the problem.

'Millions recovered'

Jim Gee, chief executive of the CFSMS, said his agency has recovered millions of pounds

He said the money, which totals almost �300m, had been freed up for spending on patient care.

We are not complacent. There is much more still to do Jim Gee, CFSMS

Speaking at the agency's annual conference in London, he said the amount of fraud being detected had jumped by 500% over the past four years.

More people are also being prosecuted. These include patients and NHS staff.

Since 1999, the agency has brought 163 criminal prosecutions of which 160 have been successful.

It has also taken disciplinary action or recovered money through the civil courts in 215 cases.

The agency played a key role in the prosecution of nurse Shauna Bowen-Thomas, from Cardiff, who defrauded the NHS of �134,000 by falsifying timesheets over two years. She was sentenced to 18 months in prison.

It has also been involved in a number of high profile cases against dentists and a senior hospital executive who were also found guilty of defrauding the NHS.

However, the agency said it still did not know how much money the NHS is losing to fraud each year. Officials are still trying to calculate that figure.

Mr Gee acknowledged that more work needs to be done.

"We are not complacent. There is much more still to do but these statistics compare very favourable with any other public or private sector organisation."

Bill Darling, chairman of the CFSMS, said: "Our aim in the coming years is not only to reduce the amount of fraud to an absolute minimum but to ensure that the NHS is properly secure for all those who work in and use it."

Unison, which represents almost 500,000 NHS workers, backed moves to tackle fraud by signing up to the NHS Counter Fraud Charter.