A report has shown patients at some hospitals are facing "unacceptably long" waits for diagnostic tests.
Patients were waiting over a year for tests, like this one looking at a gallbladder
The Healthcare Commission's report is a snapshot of the situation across England last September.
But one of the trusts which fared worst in the survey stresses it has made significant progress in reducing waits since then.
Walsall Hospitals NHS Trust was recorded as having some of the longest waits for some diagnostic tests.
As of September 30, 2005, patients needing a routine gastroscopy - where the stomach and gullet is examined - were waiting 638 days, while those needing a flexible sigmoidoscopy - where the large intestine is checked - waited 604 days and those needing a colon examination waited 772 days - over two years.
But Sarah Smith, director of development at the trust, said: "We have seen a dramatic reduction. In all three of those areas, waits are down to under six months.
"We don't have an issue any more.
"The trajectory we are on is to meet the 18-week target in 2008."
Ms Smith said investment from the local primary care trust had helped them reduce the numbers waiting, as had working with local GPs to discuss which patients needed to be referred.
"GPs here have direct access to the list. We worked with the doctors to validate who needed to be on the list and introduced a more systematic referral process so people knew who should be referred."
And the trust says that it has met the 13-week target for MRI and CT scans.
Ms Smith said the trust was aware it had a problem with endoscopic test waits before the Healthcare Commission carried out its audit, but the watchdog's advice had been useful.
However, she said making the data public almost a year later had less relevance.
"Like all trusts, because of the 18 week target, we have been putting significant efforts into reducing our waiting times.
"The Healthcare Commission data is very out of date. In that respect, this is bad timing. It is not helpful at this time."