'Such big jumps need analysis. Are employers becoming more lax in their approach? Or is it just a statistical anomaly?'

The revelation that just 4 per cent of health sector job applicants who failed criminal record checks had their job offers withdrawn raises fresh questions about the vetting of NHS staff (see 'Criminal checks fail to exclude staff').

The government is already reviewing vetting procedures in the wake of the attempted terrorist attacks in London and Glasgow in June.

Last year 1,355 people with records were still allowed to take up their posts.

Checks with the Criminal Records Bureau affect many NHS posts. The checks flag convictions, cautions, reprimands, bans on working with children or vulnerable adults and police intelligence.

The breadth of information gathered no doubt includes large swathes of petty offences, from youthful high spirits to convictions for minor offences which have no bearing on someone's fitness to work in the health service.

But there is still cause for concern. The proportion of health staff being checked for a job offer and found to have a record almost doubled to 11 per cent between 2005 and 2006, while the proportion of those subsequently blocked fell by three-quarters to just 4 per cent.

Such big jumps in such a short period need analysis. Are employers becoming more lax in their approach? Is it a reflection of a more sensible assessment of the importance of low-grade offences? Or is it just a statistical anomaly?

The difficulty in coming to an informed conclusion is that no national data is published about the offences committed by applicants who do get a job offer.

At a time when the NHS is trying to reassure the public that its vetting procedures are robust and protect the interests of patients, greater transparency is required to maintain confidence - but without triggering a witch hunt.