Companies in countries worldwide may be toying with the idea of implementing shorter working weeks, but in Greece employees have been told that, henceforth, they can put in a sixth day of labour in an unorthodox step aimed at turbocharging productivity.

After outpacing other Europeans in terms of economic growth, the nation once at the heart of the continent’s worst financial crisis has bucked the trend again, introducing a 48-hour working week. The measure, decried as “barbaric” by unions, takes effect from Monday.

“It makes no sense whatsoever,” said Akis Sotiropoulos an executive committee member of the civil servants’ union Adedy. “When almost every other civilised country is enacting a four-day week, Greece decides to go the other way.”

The pro-business government of the prime minister, Kyriakos Mitsotakis, says the initiative was made necessary by the twin perils of a shrinking population and shortage of skilled workers. Prior to announcing the legislation – part of a broader set of labour laws passed last year – Mitsotakis described the projected demographic shift as a “ticking timebomb”. In an unprecedented exodus, about 500,000 mostly young educated Greeks are estimated to have emigrated since the near decade-long debt crisis erupted in late 2009.

The six-day scheme, officials say, will only apply to private businesses providing round-the-clock services. Under the extended working week, staff in select industries and manufacturing facilities will have the option of working an additional two hours a day or an extra eight-hour shift, rewarded with a top-up fee of 40% added to the daily wage.

Either choice, the centre right government claims, will redress the issue of employees not being paid for overtime while also tackling the pervasive problem of undeclared work.

“The nucleus of this legislation is worker-friendly, it is deeply growth-oriented,” Mitsotakis said before the Greek parliament endorsed the law. “And it brings Greece in line with the rest of Europe.”

But the backlash has been fierce. In a country with almost no tradition of inspections in the workplace, critics contend the reform ultimately sounds the death knell of the five-day working week, not least because it enables employers to dictate whether a sixth day of labour is required.

For opponents, who have already taken to the streets in protest, the reform erodes legal protections and rolls back long-established workers’ rights in the name of flexibility.

“In reality this has been passed by a government ideologically committed to generating ever bigger profits for capital,” said Sotiropoulos. “Better productivity comes with better work conditions, a better quality of life [for employees] and that, we now know, is about less hours not more.”

The measure, he said, had been made possible partly because trade unions had also seen their power wane as a result of debt-stricken Athens enacting austerity measures in return for rescue funds during the country’s financial crisis. Unions have long argued that overtime enables employers to hold back on hiring more staff.

Trialled four-day week programmes have repeatedly shown increased levels of productivity with researchers attributing the outcome to improved levels of focus. Belgium in 2022 legislated to give employees the legal right to spread their working week over four days instead of five, and pilot schemes have been carried out in countries including the UK, Germany, Japan, South Africa and Canada.

Greeks already work the longest hours in Europe, putting in an average 41 hours a week according to the EU’s statistics agency, Eurostat, although surveys have also proved they get paid much less. The left-wing opposition has frequently decried “Bulgarian salaries in a country of British prices”, claiming the phenomenon has only exacerbated the brain drain.

People on pensions, who have also been encouraged to work under the legislation, have weighed into the debate.

“What the government is essentially saying is ‘go and work longer, we’ll turn a blind eye even if you’re a pensioner,’” said Grigoris Kalomoiris who heads the union of retired teachers (Pesek).

“It knows that the majority of Greeks, on an average monthly salary of €900, can only survive until the 20th of the month. This latest barbaric measure is not going to solve the fundamental problem of labour shortages and a lot of us feel it is very unfair to unemployed young Greeks who may never have a job.”