Across the European Union, 47.5 percent of unemployed people in 2013 had been so for over a year, according to data published last month by Eurostat. In Greece, this figure rose to 67.5 percent.
"The longer the time unemployed stay out of work, the more discouraged they become," Milas told CNBC.
How real is the euro zone recovery?
"At the same time, whether we want it or not, potential employers appear more willing to offer interviews (let alone hire) to unemployed who stay out of work for a shorter spell."
Guglielmo Meardi, professor of Industrial Relations at Warwick Business School, said the persistently poor labor market performance - especially in southern Europe – raised questions over these countries' policies.
"It is by now clear that freezing wages and liberalizing labor markets, by themselves, do not help," he told CNBC, stressing that disparity between the countries continues.
Unemployment in the euro zone is highest in Greece and Spain, where it is at 25.3 percent. By contrast, in western European countries like Austria and Germany, unemployment is at just 4.9 percent and Germany 5.1 percent respectively.
"The EU has to take some difficult decision, either on plans to support growth in depressed regions through demand, and not only supply policies, or on socially and politically sustainable ways to facilitate worker mobility between regions," Meardi added.