Better patient safety data needs to be collected as a matter of urgency because 'the NHS currently lacks measures of patient safety that allow national and local comparisons', Dr Foster Intelligence has warned.

A report accompanying its 2007 hospital guide How Healthy is Your Hospital? says safety is the most significant area of concern. It cited as an example the low number of trusts which supplied data to show they isolated more than 90 per cent of MRSA patients.

'Many trusts have screening and isolation policies, but do not gather data to monitor implementation,' it says. This was despite an 'increasing public appetite for assurance' over the safety of hospital care.

For the first time this year Dr Foster analysed performance against safety indicators but the results are 'put in doubt by concerns over the quality of coding of secondary diagnoses'.

This suggests that 'it is not possible to make a valid comparison between results for individual trusts - a hospital which appears to be 'less safe' may in fact be better at recording information'.

It concludes: 'Trusts need effective systems to collect data regarding compliance with their own policies in order to understand whether they are meeting best practice.'

This year's guide contains data showing that patients are twice as likely to die in hospitals with the highest mortality rates than they are in those with the lowest.

A study in the journal Heart has found that publishing surgeons' death rates will improve their performance. Researchers studied 30 surgeons who performed nearly 26,000 coronary artery bypasses in the North West.

Death rates fell from 2.4 to 1.8 per cent from 1997-2001, when results were not published, and 2001-05, when results were made public. There was no evidence surgeons were taking on less-complicated cases to improve results.