Up to 42 per cent of health trusts in England have reportedly been caught out "embellishing" their performance records, after officials used "lie detection software" to analyse their self assessments.
Last night, a health watchdog denied there was anything "sinister" about equipment it used to assess the state of the country's health service, despite claims over 230 trusts out of 570 were found to have put a gloss on their results.
In its first annual 'health check', the Healthcare Commission used a system which compares information sent from the country's trusts with its own data.
If there are any disparities between both sets of information, officials at the independent health regulator are alerted, and carry out further investigations.
A total of 42 per cent of the 570 trusts in England had been found by the new system to have "embellished" their own assessments, reports have claimed.
But a Commission spokes-woman said: "We're not trying to catch trusts out, there's nothing sinister about it, we're just checking what's happening across the trusts.
"We devised this system, which uses more than 200 pieces of information about the trusts, to identify any variances.
"If there are a number of issues or variances that need to be addressed, then a red light will flash up, and if we have any concerns then we will inspect that trust."
The study carried out by the Commission rated 21 out of 56 (38 per cent) NHS hospitals, primary care trusts (PCTs), ambulance services and mental health providers in the Midlands as 'weak'.
The new rating technique replaces the old star system with a four-point scale from 'excellent' to 'weak', and measures trusts quality of service and use of resources against 40 core standards and targets.
University Hospital Birmingham NHS Foundation Trust was the region's top rated organisation scoring 'good' for service and 'excellent' for its financial management.
But PCTs across the region appeared to take the brunt, with 12 out of 29 rated as 'weak', with three Sandwell PCTs also scoring 'weak' for service. Both Oldbury and Smethwick, and Rowley Regis and Tipton PCTs failed to meet the basic core standards, set out by the Commission.
Richard Nugent, chairman of the newly-merged Sandwell PCT, said: "The 'weak' ratings for our trusts' quality of services were primarily a result of our transition from three trusts into one.
"Because of the timing of this merger into a single management structure, we were unable to provide adequate assurance in certain areas.
"Throughout the health check process, we felt assured that we provided an honest and transparent assessment of the status of the three PCTs.
"Nevertheless, it is disappointing to have received so many 'weak' ratings for Sandwell PCTs." Mid Staffordshire General Hospitals, Dudley Group of Hospitals and Sand-well and West Birmingham Hospitals NHS Trust also failed to meet core standards on infection control and decontaminating medical equipment.
Staffordshire Ambulance Service, which fought to maintain its independence from a merger with three Midland ambulance trusts, also received a 'weak' rating.
Chairman Robert Lake said it was "regrettable" that under the new scoring system the trust "is not judged to have done so well".
But West Midlands Ambulance Service was dealt a double 'weak' score, making it the worst in the region.
Anthony Marsh, chief executive of the new regional West Midlands Ambulance Service, said: "We will continue to work towards achieving the highest standards of patient care, and I am confident the patient experience will be reflected positively in next year's assessment."
Liberal Democrat MP John Hemming (Birmingham Yardley) said: "The biggest problem for the health service in Birmingham is the last minute cuts imposed by the Government at the end of the last financial year.
"There has been too much change, which is still ongoing, at all levels of the health service but particularly in acute and primary care services. The reality of all this is staff struggling to provide best possible care on reduced resources."
Some of last year's top rated trusts, including Birmingham Children's Hospital and the Royal Orthopaedic Hospital, saw their ratings slip under the new system.