Most people who fail criminal background checks while applying for NHS roles are being allowed to keep their jobs.

More than one in 10 people who applied last year for health sector jobs that are subject to Criminal Records Bureau checks - primarily posts involving working with children or vulnerable adults, or positions of trust - were known to police.

This means they had been convicted of a criminal offence, received a police caution or reprimand, were banned from working with children or vulnerable adults, or that police had 'soft intelligence' related to the jobs they would be doing.

But only a tiny minority - 4 per cent - had their job offers withdrawn after their backgrounds were discovered.

The remaining 1,355 continued to work in the health sector with potential access to patients, according to a MORI poll commissioned by the Criminal Records Bureau and published last week.

Figures include NHS and independent and voluntary sector posts.

Patient Concern co-director Roger Goss said that the numbers were 'outrageous'.

'I'm amazed that 96 per cent of staff with CRB records are being taken on. It puts one off having any medical care or going near medics.

'I want to know the justification for every single person taken on in these circumstances,' he said.

The most common reason for a job offer being withdrawn was details of previous convictions, followed by local police information and, last, being banned from working with vulnerable adults.

No information was available for those who kept their jobs despite having police records.

The proportion of prospective health workers with a 'not-blank' CRB record has almost doubled in a year, from 6 per cent in 2005 to 11 per cent in 2006. The number of job offers withdrawn as a result of CRB checks has significantly dropped, from 17 per cent to just 4 per cent.

NHS Employers deputy director Sian Thomas stressed that the definition of a 'not-blank' record was very broad. 'It would be dangerous to imagine that all of these people had convictions,' she said. 'They may just have been cautioned, and the check goes right back to when the person was a juvenile.'

The release of the poll coincided with the publication of the Criminal Records Bureau's annual report.

Launching the report, home office minister Meg Hillier said that in the light of recent terror plots allegedly involving NHS staff, it was down to employers to vet staff properly. She said: 'CRB can only check what's out there, when there's proof that someone's done something.'

Regarding overseas staff, she said: 'Employers have to be convinced that their checks are good enough to satisfy their demands for safety in the health service.'

But Ms Thomas said it was up to the Home Office whether foreigners were given work permits.