One third of hospitals serve sub-standard food to patients or leave them hungry, the Government's public spending watchdog said yesterday.

Inspectors uncovered an array of cases of vulnerable patients missing out on meal-times because of chaotic arrangements in hospitals.

The Audit Commission estimates the unserved meals are costing the health service £18m. The report found that some dishes were served cold because one member of staff struggled to hand out all the meals, while some patients did not receive the meal they ordered as they were at the end of a "food run" and their choice had gone. Others were unable to eat because they could not reach their meals, open them or use the cutlery.

The report said: "Elderly patients are not always given the assistance they need to feed themselves and, in many hospitals, no one checks how much they have eaten. Maternity patients often miss the set meal times and may go without food for long periods."

The commission said that 23 per cent of trusts failed to check new patients' dietary requirements, despite its importance to their recovery. One third of dieticians acknowledged hospital menus were "inadequate" and did not meet patients' needs.

The NHS spends £275m on hospital catering and produces 220 million meals but the commission uncovered a "staggeringly wide" variation, from £2.80 to £20, in daily spending on patients. It estimated that the wastage from unserved meals could be cut by £8m a year.

The report concluded: "Patients' nutritional needs are not always identified or fulfilled due to limited menu choice, poor timelines of meals or lack of assistance." The Commission's survey comes before the Government launches its Better Hospital Food programme, featuring a national NHS menu drawn up by TV gourmet Loyd Grossman.

The Health Secretary, Alan Milburn, has promised patients would witness "very real benefits in the coming months".

A Department of Health spokesman said: "We are aware a number of patients enter hospital malnourished as a result of their illness and that some also leave hospital malnourished. That is not acceptable."

The Audit Commission controller, Sir Andrew Foster, said: "These are not problems that will be solved by throwing money at them. It is essential that all staff in the catering chain work together."