Some doctors in Oxfordshire are undermining Tony Blair's flagship scheme to allow patients to choose which hospital to undergo operations in, a study has revealed.

But the proportion of survey respondents who said their GP had offered them a choice of local hospitals for diagnosis was significantly higher in Oxfordshire than in many other parts of the country.

The survey of 270,000 patients across England found 48 per cent of patients in North East Oxfordshire said they were allowed to pick their hospital.

In South East Oxfordshire the figure was 50 per cent, in Oxford 55 per cent, and South West Oxfordshire PCT 61 per cent. Cherwell Vale offered the highest proportion of patients a choice - 63 per cent.

The county's GPs performed much better than the country as a whole, where overall about a third of patients were given a choice. The Department of Health has pledged to ensure patient choice is not denied.

The survey was carried out in July, before the five trusts merged to form Oxfordshire Primary Care Trust. It was unclear whether GPs were deliberately keeping patients in the dark, or putting so little emphasis on the choice available that patients forgot what was said.

Oxfordshire Primary Care Trust said it had worked closely with GPs to provide information to patients about the "choice initiative".

Spokesman Catherine Mountford said: "We are pleased that patients are becoming aware that they have a choice of where to go for their treatment and across Oxfordshire we have performed well against the national target."

The scheme allows patients a choice of at least four hospitals for an operation, but relies on GPs telling people about the scheme.