More than a quarter of hospital trusts in England are at increased risk of providing poor levels of care, according to a new report.
Monitoring by the Care Quality Commission (COC) found that 44 of 161 hospitals are in two of the highest categories for care failings.
The study was organised as part of the body's new inspection programme for hospitals, which will see all trusts checked between now and 2015.
Inspections begun during September and it is estimated that 18 will have been completed before the festive season.
The CQC said it is not using the data from this latest analysis to pass full judgements on trusts, but it is using the data to determine which inspections need to be prioritised.
Professor Sir Mike Richards, the CQC's chief hospital inspector, said the review will work as a kind of screening.
"Our intelligent monitoring helps to give us a good picture of risk within trusts, showing us where we need to focus our inspections," he explained.
The first two risk bands cover hospitals deemed to be high risk and include 24 and 20 trusts respectively.
Of those in band one, 11 trusts are already having to carry out special improvement measures following unusually high rates of mortality.
South London Healthcare NHS Trust was found to be the most risky trust with an overall score of 0.14.
That was followed by Croydon Health Services at 0.13, Basildon and Thurrock and Barking, Havering and Redbridge at 0.12.
Jamie Reed, Labour's shadow health minister, said the coalition government should be ashamed that so many of its hospitals are in the position they are.
He added the prime minister has "siphoned £3 billion out of the NHS front-line to blow on a back-office re-organisation nobody voted for.
"Hospitals were left on a financial knife-edge and they are clearly struggling to maintain standards of patient care after more than three years of chaos."
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