The country's healthcare system is being supported by 1.9 million volunteers, worth almost £500 million to the NHS, according to a new study.
Research by older people's charity Royal Voluntary Service found that the contribution of its own hospital volunteers was worth £2.75 million alone.
Chief executive David McCullough said: "The help provided by volunteers to the health service mustn't be underestimated. Although their work may be simple, it is a source of vital support and we know that the emotional benefits volunteers offer to patients can make a real difference to wellbeing.
"However, to continue to help more people during a hospital stay or on a return home, we need more volunteers to come forward and dedicate just a couple of hours a week, or whatever they can."
The report, based on a survey of over 2,000 adults, was published to mark Volunteers' Week, which runs this week.