Europe is scrambling for ideas on how to detain and process the hundreds of thousands of migrants winding through the continent, yet after months of effort officials are still struggling to make headway before the onset of winter.

Heads of government agreed to come up with 100,000 places in shelters along the so-called western Balkans route after European Commission president Jean-Claude Juncker warned that refugee families could “perish miserably” during the journey from Greece through former Yugoslavia and into Austria and Germany without help.

At the moment, officials are suffering from a dearth of information on the ground as Greece and countries in former Yugoslavia — which often have strained diplomatic relations — either do not collect or fail to pass on information.

“I cannot tell you how many are on the move as we speak,” said one EU official.

Berlin has heaped pressure on its neighbours to deal with incoming asylum seekers before they reach German borders, as chancellor Angela Merkel attempts to quell a domestic backlash — among both voters and her own party — against the influx of refugees.

EU leaders have various models to hold asylum seekers — from migrant camps and reception “hotspots” to Germany’s ideas for transit zones — but have hit a wall of political objections, legal pitfalls and logistical shortcomings.

Under the proposals agreed on Sunday, Greece will become a temporary de facto refugee camp for the rest of the EU, with 30,000 places set up by the end of the year — despite vociferous opposition from Greek officials in the past.

Another 20,000 places for asylum seekers will be provided in makeshift accommodation — such as Greek people’s homes. These extra places will be backed by the UN refugee agency UNHCR and funded by the EU.

Ms Merkel is banking on the extra reception places in Greece — coupled with the EU’s controversial plan to relocate 160,000 asylum seekers throughout Europe — to bring order to the situation despite doubts from both officials and experts over whether the scheme will work.

People will have their asylum applications assessed in Greece before being sent to other countries in the EU as part of the bloc’s controversial plan to relocate 160,000 asylum seekers, which has stuttered since its introduction in September.

National capitals have so far put forward fewer than 1,000 of the proposed 160,000 places, meaning that Greece risks becoming a bottleneck for asylum seekers.

Frontex, the EU’s border agency, estimates nearly 500,000 people have arrived on Greek islands this year.

So far, only a few dozen people have been relocated under the scheme as asylum seekers prove reluctant to take part either because they do not trust EU officials and fear being deported, or because they are unwilling to head to any country other than Germany.

In Brussels, officials have taken a firm line. “Migrants need to understand you cannot come to the EU and choose where you go,” said one.

But on the ground, officials have promised asylum seekers trips to richer countries, such as Sweden, in order to encourage take-up of the flagship policy, according to people familiar with the situation.

This situation will become acute when these sought-after places run out, leaving asylum seekers facing relocation to countries in eastern Europe — some of whom vociferously opposed the scheme.

As a result, “migrants think they are better off walking on the western Balkans route”, said an EU official.

Serbia, for instance, has about 2,500 reception places spare, which people are unwilling to use for fear that they will end up stuck in Serbia.

“We have to convince them,” said the official. “They have to see it working.”