The EU has been strongly criticised over conditions in Greece’s largest refugee camp, where Oxfam reported women are wearing nappies at night for fear of leaving their tents to go to the toilet.

The British-based NGO described the increasingly dangerous state of the EU-sponsored Moria camp on the island of Lesbos, where a 24-year-old man from Cameroon was found dead in the early hours of Tuesday as temperatures fell below freezing.

Under a landmark deal agreed between the EU and Turkey in March 2016 to reduce the number of people arriving into the continent, refugees seeking asylum on Greek islands have been forbidden from leaving “hotspot” camps to travel to the mainland.

Jean-Claude Juncker, the European commission president, has hailed the deal as a success for thwarting smuggling gangs and reducing migratory flows.

But as a result, about 15,000 men, women and children are stranded in Lesbos, Chios, Kos, Samos and Leros, the islands closest to Turkey.

The report from Oxfam titled Vulnerable and Abandoned highlighted the failure of authorities at the Moria camp, where nearly 5,000 people live, to identify vulnerable refugees who are eligible for help.

Since the resignation in November of the government-appointed doctor designated to make assessments of asylum seekers’ wellbeing, Oxfam claimed these failed to take place for at least a month at Moria, which at times last year was home to three times the number of people it was designed for.

As a result, Oxfam warned “vulnerable people including survivors of torture and sexual violence are being housed in unsafe areas … Pregnant women and mothers with newborns are left sleeping in tents, and unaccompanied children, wrongly registered as adults, have been placed in detention.”

For many people in the camp, burning plastic bags and bottles is the only way to keep warm, Oxfam said. Photograph: Giorgos Moutafis/Oxfam

Mothers are said to have been sent away from hospital to live in a tent as early as four days after giving birth by caesarian section, in a camp where fights break out regularly and two-thirds of residents say they never feel safe.

“In a few extreme cases, women say they have resorted to wearing diapers at night to avoid having to go to the toilet after dark,” the report said.

One woman, 36, from Cameroon, told Oxfam that people were randomly attacked at the camp.

“Moria is a dangerous place for women,” she said. “Fights can start at any moment. At any moment you can expect a stone to your head, even if you’re just walking to the toilet or to your tent … I live in the closed section for women who are alone, but after 11pm the door is open, and anyone can come in because there is no security guard at night. Safety is a big issue for us.”

A 24-year-old woman from Afghanistan said: “In the winter there is no warm water. We take showers over the toilet.”

Renata Rendón, Oxfam’s head of mission in Greece, said: “It is irresponsible and reckless to fail to recognise the most vulnerable people and respond to their needs.

“Our partners have met mothers with newborn babies sleeping in tents, and teenagers wrongly registered as adults being locked up. Surely identifying and providing for the needs of such people is the most basic duty of the Greek government and its European partners.”

Rendón added: “European leaders have to face the fact that their current policy is perpetuating an inhumane reception system and putting refugees at risk. Rather than continuing to focus all their efforts on returning refugees to Turkey under the deal struck in 2016, EU member states should support Greece to improve conditions in the island camps and move people off the overcrowded islands and on to the mainland.”

People seeking asylum are normally expected to undergo vulnerability assessments soon after arrival on the islands, but the medical and psychosocial screenings at Moria have been described as cursory at best due to a “severe shortage” of staff.

Oxfam reported that for “many months”, there was just one doctor employed by the Greek government at the camp to assess the health conditions of as many as 2,000 new arrivals in one month, before the medic eventually quit.

Even refugees identified as vulnerable and theoretically allowed to leave the islands are being trapped due to a lack of accommodation on the mainland, it is claimed.

At points in 2018, the camp housed three times the number of people it was designed for. Photograph: Giorgos Moutafis/Oxfam

According to UNHCR, the UN refugee agency, more than 4,000 people eligible for transfer were stuck in Lesbos and Samos in November.

The slow asylum application process is also said to be condemning families to years in the camps, where people live in tents without hot water and electricity during winter.

“Due to a lack of staff, many people who arrive now in Lesbos have their first asylum interview scheduled for 2020,” Oxfam reported.

For some, open fires are reportedly the only way to keep warm in winter. The burning of plastic bags and bottles is said to create a “dangerous, smoky, acrid atmosphere”.

Three asylum seekers died of carbon monoxide poisoning in the camp in January 2017 while trying to stay warm with makeshift stoves.

Since September, about 11,000 asylum seekers have been transferred by ferry and coach to hotels and apartments on the mainland in an EU-funded scheme overseen by UNHCR.

Stella Nanou, a spokesperson for the agency in Athens, said: “While efforts have been intensified to transfer people and Moria’s population has fallen below 5,000 for the first time since April last year, it is still twice over capacity.

“There are people, vulnerable people, families and children, living in totally unsuitable conditions in the biting cold. We’re talking about human beings. The situation is very bad, very grave.”

A commission spokesman said it had made €289m (£260m) available to the Greek government to “support migration management” and was following the situation on the Greek islands closely as the weather deteriorated.

“We have repeatedly alerted the Greek authorities about the very challenging situation in the Greek islands and pointed to the urgency to address this situation, while always ensuring the availability of EU funds to help face those challenges,” the spokesman said.

“Of course, the overall responsibility for managing migration flows in Greece, including in the hotspots, rests with the Greek administration. The commission provides support; it does not replace the Greek authorities.

“There is in particular an urgent need to winterise reception capacity and to decongest the islands by accelerating asylum procedures and increasing returns in parallel to the ongoing efforts to transfer those migrants to the mainland whose geographical restrictions have been lifted.”