A list of 19 questions patients should ask before having surgery to ensure they get the best treatment is proposed today by the head of theNational Audit Office, the independent watchdog on government spending.

Sir John Bourn includes the list in a report on hip replacements that exposes wide variations in the care provided to patients in different parts of the country. Sir John found evidence of discrimination against patients who were excluded from surgery on the grounds of their age or weight.

The questions cover the surgeon's success rate, the risks, for how long the surgery is likely to be effective and what other options there are. With slight adaptation, it could be used for any operation.

An investigation by the audit office found one in 12 consultants imposes an upper age limit for new hips of 90 to 95 - despite the fact that the Queen Mother, who is 100 this year, has had both hips successfully replaced in the past five years.

One in three consultants refuses surgery to people who are overweight, on the basis that a new hip would not last. However, the weight limit imposed by different consultants varies widely, from 14 stone to 20 stone. The report says: "This calls into question the equity with which patients are considered for surgery and implies that in some cases whether or not a patient is offered surgery depends on which consultant he or she sees."

About 8 million people suffer hip pain, usually caused by arthritis, and the NHS does more than 30,000 hip replacements a year at a cost of £139m. The report says it is "a highly effective procedure, producing immediate and dramatic benefits in almost all cases". However, between 10 and 20 per cent of patients suffer complications, including infection and loosening of the joint, which may require a repeat operation. These are more complex, more expensive and less successful.

The best chance of success lies with an experienced surgeon but the report found 71 per cent of consultants performed fewer than 10 repeat operations a year and one in 12 performed fewer than 10 initial operations. "This may be insufficient to ensure outcomes are maximised," says the report, "Hip Replacements: getting it right first time".

Fewer than half of consultants monitor the success of their work by checking the rate of re-operation, the incidence of infection or the proportion of patients free from pain. The report says this is a "matter of concern" and warns that, without monitoring, problems may not be picked up.

An example of what can go wrong involved the 3M Capital hip used between 1991 and 1997 in 4,700 patients. It turned out to have a failure rate as high as 20 per cent and in 1998 the Department of Health issued a hazard warning and all patients were recalled for checks.

More than 60 artificial hips are in use, costing between £300 and £2,000. The choice of device rests with the individual surgeon but the original design introduced by John Charnley in the 1960s has proved difficult to improve upon.

Under new guidance to NHS trusts published last week, the National Institute for Clinical Excellence said only those shown to last at least 10 years with a failure rate of no more than 10 per cent should in future be used. Newer devices should be used only as part of a clinical trial. The ruling is expected to reduce by more than half the number of devices used.

Two in 10 heart patients say doctors fail to consult them over their care or to explain the treatment, a national survey of NHS patients, conducted for the Department of Health, has shown. Patients said doctors talked about them as if they were not there, did not tell them what was going on and did not involve them sufficiently in decisions about their care.

Gisela Stuart, Health minister, said: "The NHS must listen to patients and give them a stronger voice."