Which? reviewed hygiene inspection reports for 50 hospitals and found evidence of cockroaches, mice and mouldy cooking equipment.
An online survey by the organisation also revealed 29% of NHS patients still felt hungry after their meals.
But the Department of Health said hospital food had improved in the last few years.
Which? said its trawl of three years' worth of hygiene reports revealed problems such as dirty equipment, cockroach infestations, lack of soap or hot water, with poor refrigeration also cropping up regularly.
Other hospitals used food fridges to store medical supplies, had out-of-date foods and failings in food safety procedures, Which? added.
But it said not all hospital catering facilities were dirty and some were highlighted for their cleanliness.
Hungry
In a separate online survey of 833 hospital patients, the consumer group also found some patients were going hungry.
Twenty-nine percent of NHS patients questioned said they felt hungry after their hospital meal compared with 4% of private patients.
Neil Fowler, editor of Which?, said: "Hospital food hasn't got the best of reputations but you'd expect the kitchens to be clean at the very least. Unfortunately, we've found this isn't always the case.
"Our survey shows a low level of satisfaction with hospital food in NHS hospitals. The government paints a rosy picture but the reality is very different, with many patients left with a nasty taste in their mouths."
A Department of Health spokesperson said: "Last month 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 with 17% in 2002.
"There are some excellent menus around but we recognise that more needs to be done. The government has made a commitment to establish nutritional standards for the NHS and this work is now under way."
source: www.bbc.co.uk
