MPs have raised concerns about the standard of some hip replacement surgery in the NHS.
Some artificial hips are unproven
The Public Accounts Committee found one in 10 consultants were using artificial hips of unproven quality.
It also found some hip replacements were more than three times as expensive as others at £7,456.
The committee has called on ministers to introduce strict safeguards to ensure high standards and value for money.
More than 43,000 hip replacements are performed by the NHS every year.
The committee said standards had improved since their last report three years ago - but there were still concerns.
Edward Leigh, the committee chairman, said: "Although there have been some welcome developments since the committee's previous report, I still have concerns about whether patients are always getting the best results they could from hip replacement surgery in the NHS."
MPs said controls were needed on the use of new types of artificial hip, which had little or no track record of effectiveness.
Their investigation found that 40% of trusts had been offered incentives by manufacturers to switch to new models - and one in 10 consultants had accepted the offers.
The committee raised concerns that half of consultants doing primary hip replacements did less than one a week - raising doubts about their ability to hone their skills.
MPs were also worried about the government's 47 new treatment centres, which will perform thousands of hip replacements a year by the end of 2005.
They fear that while the centres will initially help to reduce waiting times, there may not be sufficient work to justify them in the future.
Mr Leigh said the establishment of a National Joint Registry to log hip operations had been welcome - but only half of NHS hip and knee replacements were currently recorded.
The NHS Purchasing and Supply Agency needed to issue a full list of prostheses that meet the published standards as soon as possible, he said.
And the Department of Health must research how many operations need to be
undertaken annually by surgeons to maintain their skills and ensure good
clinical outcomes are achieved.
Health Minister John Hutton said the NHS had undertaken a significant programme of work on improving the quality and accessibility of hip replacement surgery.
He said: "This is reflected in the increase in the number of patients undergoing hip
replacements with an additional 6,000 patients being treated in 2002-03 compared
"The National Joint Registry will in future show whether the performance of hip replacements meet the NICE standard of effectiveness.
"Participation in the NJR continues to grow - in April 2003, 1,253 operations
were entered on the NJR but this had risen to 9,445 in March 2004 - and we're
encouraging even greater compliance.
"The department is also considering whether surgeons carrying out hip replacements should carry out a minimum number of operations."
Gordon Lishman, Age Concern director-general, said: "We are extremely worried about the findings of this report, which indicate that patients are not always getting the best results from hip replacement surgery.
"We now have very clear guidelines from the National Institute for Clinical Effectiveness.
"Every patient deserves the most effective treatment and there can be no excuse for these guidelines not being followed for every operation."