Tameside Hospital has been warned in a national report that its death rates could be 17 per cent higher than they should be according to indicators.
The Dr Foster Hospital Guide assessed the trust as the third worst performing in England for deaths up to 30 days after treatment.
The tenth annual report from the body introduced a new Summary Hospital-level Mortality Indicator (SHMI), which it said looked at a range of factors and examined deaths that occurred up to 30 days after treatment.
The report said: "We are featuring four measures of mortality in this year's hospital guide.
"All these measures should be used as 'red flags' or warning signs. They indicate that there is a risk that poor-quality care is leading to higher than expected mortality; they do not prove that this is happening.
"We only apply these analyses to NHS acute trusts."Tameside Hospital Medical Director Tariq Mahmood said: "We welcome the Dr Foster report and take its findings very seriously.