The Food Watch survey of 2,240 patients in England found more than a third had abandoned their food, and 40% have had food brought in by visitors.
Around 26% who needed help with eating did not receive any, it added and 22% found their meals too hot or too cold.
The Commission for Patient and Public Involvement in Health is calling on the government to improve food standards.
Some 18% of those questioned said they did not always have their choice of meal, and 81% said they had no choice of meals in advance.
'Disappointing'
The report was conducted by Patient and Public Involvement Forums at 97 hospitals across England. Sharon Grant, chair of the Commission for Patient and Public Involvement in Health, said the findings were "disappointing".
"Proper nutrition is essential to recovery both physically and psychologically," she said.
"Patients have every right to expect food that is nutritious, served at the appropriate temperature, meets their dietary needs and help to eat if they need it."
"Not only will this impact upon a patient's recovery, but is a huge waste in terms of NHS money and resources," she added.
Ms Grant said the survey had revealed examples where the food was of a good standard, but the forums had been shocked by the comments from some patients.
She added the findings would be sent to Health Secretary Patricia Hewitt in a bid to improve standards across the board.
Age Concern England director general Gordon Lishman said hospitals needed to urgently address the problem.
"This survey is further damning evidence that many hospitals are putting lives at risk by failing to provide patients with basic care.
"It's a fact that malnourished patients stay in hospital for longer, are three times as likely to develop complications during surgery and have a higher mortality rate."
But health minister Andy Burnham said hospital food had improved significantly over the past few years, although he said more action was needed.
He added: "Earlier this week the independent Healthcare Commission found that nearly all trusts (over 96%) were meeting the core standards on hospital food.
"Last year, the independent Patient Environment Action Teams found that 90% of hospitals were rated good or excellent for food standards compared to 17% in 2002."
source:www.bbc.co.uk
