There should be "mandatory minimum standards" for hospital food, Labour has said.
Official NHS Digital data shows that in 2016/17 some hospitals in England are spending £3 on each patient per day for their meals while others are spending up to £40.
But there are discrepancies in the way the data is calculated, some hospitals are providing data based on one meal, while others are supplying the amount spent on two or three.
Labour said that official standards for hospital food, such as those observed in schools, would ensure that patients are given nutritious meals.
Such standards may also lead to more transparency over where the money is being spent.
In a speech to the Hospital Caterers' Association annual conference in Newport on Thursday, Labour's shadow health secretary Jonathan Ashworth will say: "Patient care isn't just about medicines, bandages, treatments and surgical procedures, its about nutrition and hydration as well.
"And yet we have allowed a situation where some hospitals, according to the official data, are spending less than £3 a day on patient meals.
"Unlike schools and prisons there are no mandatory minimum requirements for hospital meals, so the next Labour government will substantially increase investment in our NHS to improve patient care including providing the nutritious meals patients deserve.
"Labour will place hospital food standards on the same legal basis as school food standards, to ensure hospitals meet mandatory minimum standards for the food served to patients, staff and visitors and these standards should be independently monitored and enforced."
Commenting on the news, Katherine Button, coordinator for the Campaign for Better Hospital Food, said: "We warmly welcome today's announcement that the Labour Party will make legal standards for hospital food part of their health policy.
"Under the earlier coalition government, food standards were introduced in NHS hospital contracts, but we know that at least half of hospitals are still not complying, and that the current Government is failing to encourage progress."
A Department of Health and Social Care spokeswoman said: "Whilst food in hospitals is given a rating of nine out of 10 by patients, we know nutrition is a vital part of recovery. That's why we have already introduced the first ever legally-binding food standards in the history of the NHS, and continue to press for high standards."