AID agencies need more than £960 million to help refugees in Greece and the Balkans this year – but have received only half of that sum.

When the multi-agency Refugee and Migrant Response Plan (RMRP) launched in January, organisers estimated they would need around £789.6m to cope with continued migration from Syria, Afghanistan, Iraq and other troubled countries.

But yesterday the sum was revised as senior figures added almost £200m more – taking the total to £960.9m.

But despite continued deaths at sea, ongoing calls from Greece for more help and continued concern from humanitarian agencies about the wellbeing and treatment of those in migrant camps, less than £471.6m has been collected.

The UN High Commissioner for Refugees, Filippo Grandi, the co-leader of the programme, said the calculations had been changed “to take into account the new circumstances on the ground” following border closures along the western Balkans route and the refugee return scheme between the EU and Turkey.

A spokesperson said fewer people are now moving into Macedonia and on through Serbia and beyond, but many more remain in Greece.

EU red tape means many are stuck in camps with inadequate sanitation, accommodation, food and medicine.

There are now serious concerns about the implications of the shortfall in funding.

A UNHCR spokesperson said: “While the measures adopted have significantly reduced the number of arrivals in Greece, over 57,000 refugees and migrants are currently dispersed across the country in several sites on the mainland and the islands.

“In this context, UNHCR and humanitarian partners have redefined their engagement from a response primarily targeting people on the move to focusing on a static population in Greece and on protection activities in countries in the western Balkans.”

Almost 4,000 people are known to have died or were reported missing in an attempt to cross the Aegean sea from Turkey to Greece last year. Turbulent winter conditions were expected to reduce the numbers attempting the journey in early 2016, but 200,000 survived the attempt between January and May – 150,000 of whom landed in Greece. Of these, almost 40 per cent were children and Greek authorities and aid groups are now struggling to care for them.

Last month former child star Heather Ripley, who found fame in Chitty Chitty Bang Bang and is currently volunteering at the Lagadikia camp near Thessaloniki, described the situation as a “time bomb waiting to explode”. Yesterday the UNHCR said: “Unmet needs remain significant as living conditions in the sites in Greece, both on the islands and the mainland, have deteriorated as a result of congestion and the rapid nature in which sites were established on the mainland.

“The affected population includes many people with specific needs, such as unaccompanied or separated children, single women, pregnant or lactating women, the elderly, people with disabilities, as well as the sick and injured.

“There is a risk that these people will increasingly rely on smuggling and trafficking networks, exposing themselves to greater protection risks, which will be even more challenging to address, considering the clandestine nature of the movement.”

UNHCR spokesperson William Spindler told The National that, as of the last update in May, the UK had contributed £18.5m to the pot, most of which – £13.9m – had gone to Greece, with smaller amounts given to FYR Macedonia, Serbia and Slovenia.