Almost 50,000 patients are dying each year in NHS hospitals in a state of malnutrition which may have hastened their end, according to a report commissioned by ministers.
The figure was seized on by the Tories, who described it as "horrific" and accused the Government of "dragging their feet".
The number affected is higher than has been previously thought. Last May, ministers reported that 239 patients had died because of malnutrition in hospitals in England in 2007.
But the report, from the Nutrition Action Plan Delivery Board, commissioned by the Government to oversee measures to improve nutrition in the NHS, said: "We believe these statistics can be very misleading.
"We know malnutrition predisposes to disease, it delays recovery from illness and it increases mortality. It follows that the effect of malnutrition on mortality rates is substantially greater than the number reported to have died because of malnutrition."
The report was delivered to ministers last August but only published yesterday. Extrapolation by the Tories suggests 47,800 people died in hospital with malnutrition in 2007.
Malnutrition is widespread among the elderly and sick, as illness depresses the appetite and makes it difficult to eat. But many patients deteriorate even after they have entered hospital.
Campaigners say there is a lack of help with eating in hospitals alongside a failure to recognise the severity of the problem.
The independent inquiry report into Mid Staffordshire NHS Foundation Trust published on Wednesday said that "about half the patients and their families who gave oral evidence provided accounts of issues with obtaining appropriate food and drink".