Thousands of homeless patients have been discharged from NHS hospitals directly back to the streets in the past five years, despite some being in recovery from major surgery and mental health crises, the Guardian can reveal.

Experts have warned of a growing humanitarian crisis in England after instances of patients leaving hospital with nowhere to go rose by nearly a third between 2014 and 2018. Thousands of homeless patients were readmitted within six months, according to figures obtained by the Guardian.

Official NHS England guidance aimed at freeing up beds was clarified in November to allow hospitals to discharge homeless patients to the streets if they are not judged to be a priority for housing or further care, despite widespread concern over the growing number of homeless deaths.

The number of homeless patients with Victorian-era illnesses such as tuberculosis, as well as serious respiratory conditions, liver disease and cancer, has surged over the past decade, according to NHS figures.

Dr Nigel Hewett, the medical director of Pathway, a healthcare charity that helps NHS trusts integrate care for homeless people into their services, said: “Hospitals don’t generally want to discharge people to the streets, but often lack the skills and contacts to negotiate the system, which expects you to prove that you are habitually resident, locally connected, vulnerable and priority need.

“The Homelessness Reduction Act [2017] imposes a new duty to refer homeless people in hospitals. But the bare minimum would be to email a person’s details to the local housing department. We believe that there should be a duty [for local authorities and NHS hospitals] to collaborate.”

Data obtained from 89 NHS trusts in England found the number of discharges from hospital of people with no fixed abode rose by 29.8% from 6,748 in 2014 to 8,758 in 2018.

Barts Health, Guy’s and St Thomas’ and King’s College hospital trusts in London recorded the most homeless patient discharges over the period. The Northern Care Alliance, which covers large parts of Greater Manchester, recorded a 206% increase in the five years, from 179 discharges in 2014 to 549 in 2018.

With rates of readmission within six months of more than 75% in some NHS trusts, the number of homeless patients discharged to the streets is likely to be about half the number of recorded discharges, as many were released more than once, although no clear statistics are available.

The figures obtained under freedom of information requests did not include details on whether a patient discharged themselves or was released by the hospital.

Jonathan Ashworth, the shadow health and social care secretary, said: “These are really quite heartbreaking figures revealing something shameful about our society today after years of austerity. There is clearly more to be done to ensure hospitals are better coordinated with local council housing departments when discharging patients.”

Stephen Robertson, the chief executive of the Big Issue Foundation, said: “This is a sign of increasing demand and decreasing resources, and it is creating a humanitarian issue, which in the worst-case scenario is producing people living and dying on the streets of their country.”

He described the findings as “shocking but not surprising”, and said a better approach would be to create a pathway for people leaving hospital. “They come in an ambulance and go back through the hospital doors perhaps to recover from something while sleeping on the street … So the likelihood and resilience from recovery can be harder. This is a sign of a system failing people.”

In November, NHS England guidance on delayed transfers of care – when a patient is judged well enough to leave hospital but is still occupying a bed – was clarified to say: “Where patients do not meet the eligibility criteria for care and support, or the local authority housing priority criteria, it may be necessary to discharge them back on to the street.”

Dr Michelle Cornes, a researcher at King’s College London, has been leading an evaluation of the government’s homeless hospital discharge fund, which was establish in 2013 in response to figures showing 70% of homeless patients were being discharged to the street.

“Discharge to the street is not only heartbreaking for the patients, who may have made enormous strides toward recovery while in hospital, but also heartbreaking for the nurses and doctors who will have cared for them,” she said.

Cornes said her research had found local examples of innovative partnerships between health, housing and homelessness services that saved the NHS money in the long run.

“These intermediate care or step-down schemes work to free up hospital beds while ensuring people have somewhere safe to stay while their housing and other issues are sorted out,” she said.

After NHS England was provided with the figures and asked about the updated discharge guidance, a spokesperson said: “The NHS is caring for the growing number of homeless people in an increasingly tailored way, including investing in more proactive outreach and mental health support for rough sleepers, and our long-term plan commits local health groups to taking more action along with local partners to tackle health inequalities facing people in their areas.

“Staying in hospital for longer than you medically need to presents a real risk to your health, but NHS staff work hard to make sure that wherever possible when someone has completed treatment, any other services that they may need are in place before they are discharged.”

A government spokesperson said: “Tackling homelessness will only be solved if partners work together effectively. The law now requires councils to provide early support for those at risk of being left with nowhere left to go and for key parts of the NHS to refer people who are homeless to councils.”