A new report has warned against returning asylum seekers to Greece.
The UNHCR paper says that access to the asylum procedure there is "challenging", with less than half of the number of regional asylum offices prescribed by law having been created.
While it also says that the asylum service is staffed at only 75%.
"While the authorities have made efforts to process the more than 37,000 appeals pertaining to cases under the old procedure, the backlog still remains," it finds.
"Persons who do not manage to file an asylum application face the risk of being detained and removed as irregular migrants. Administrative detention is generally applied without an individual assessment or considerations of alternatives to detention".
It also says that procedural guarantees are often not properly implemented, resulting in "arbitrary detention in difficult conditions."
It finds that while a 'first reception service' was established in 2011 with the objective of finding a process for the identification of asylum seekers with specific needs, only one facility exists - along with and two mobile units.
During 2012, 9,577 asylum applications were submitted to the police under the old asylum procedure by persons mainly from Pakistan, Bangladesh, Georgia, Afghanistan and Albania.
In 2013, that number dropped to 3,407.
But the paper concludes that: "In light of the situation described above, UNHCR continues to advise Governments to refrain from returning asylum-seekers to Greece."
The UNHCR adds that it is ready to continue working with the Greek authorities to address the "ongoing challenges and encourages EU member states and institutions to lend their support, including financial support, to ensure the sustainability of these efforts".