Greece's parliament on Wednesday debated a controversial reform proposed by the conservative government, which would allow 13-hour workdays under exceptional circumstances, drawing fire from unions and opposition parties.

Unions have staged two general strikes against the reform this month, the latest on Tuesday, with thousands of workers protesting a bill "worthy of the Middle Ages," according to the left-wing Syriza party.

The government insists that the 13-hour workday is optional, only affects the private sector, and can only be applied up to 37 days a year.

"We are now giving the possibility (to an employee) to perform this extra work for the same employer, without commuting, with increased pay of 40 percent," Labour Minister Niki Kerameus argued in Parliament.

In a country where the economy has recovered since the debt crisis but remains fragile, this possibility already exists, but only if an employee has two or more employers.

The reform is seen as targeted towards Greece's services sector, especially during the busy summer tourism season, enabling employers to avoid hiring additional staff.

But opposition parties and unions argue that workers will risk layoffs if they refuse longer hours.

"Our health, both mental and physical, and the balance between personal and professional life are goods that cannot be replaced with money," Stefanos Chatziliadis, a senior member of civil service union ADEDY, told AFP during a Tuesday protest in Thessaloniki.

"Making it legal to work from morning till night is not normal and cannot be tolerated by our society. It is truly barbaric. It is inhuman," he said.

- Voluntary –

The legal working day in Greece is eight hours, with the possibility of performing paid overtime.

The new law is expected to be passed by parliament at a Thursday vote, where the ruling conservatives have 156 MPs in the 300-seat chamber.

Syriza leader Sokratis Famellos said the government "is establishing a true Middle Ages of labour."

However, Greece's labour minister criticised the "misleading use of the term '13-hour workday'" as it "suggests that everyone would work 13 hours a day."

It is a provision that will only be valid "up to 37 days a year, or about three days per month," and on a voluntary basis, she stressed.

Private and public sector employees have twice taken to the streets to denounce the "worsening of an already deeply problematic situation," according to the General Confederation of Greek Workers (GSEE).

It claims that many employees will be unable to refuse to work 13 hours, given the "unbalanced power dynamics between employer and employee, reinforced by the precariousness prevailing in the labour market."

- Violated –

Unions believe the right to a mandatory daily rest of 11 hours will be at risk, largely due to the time spent commuting to work.

"Working 13 hours a day means there is absolutely no free time left to lead a somewhat decent life: spending time with friends, family," said Dimitris Polyzoidis, 37, a technician at the Thessaloniki protest.

Sofia Georgiadou, 29, a store employee, denounced "a new attempt to legalise modern slavery."

"You can't really refuse; they always find ways to impose what they want," said Maria, a 46-year-old construction company employee.

According to Eurostat, Greeks already work 39.8 hours a week on average compared to the EU average of 35.8 hours.

The average working time hides significant disparities, and wages remain particularly low.

Servers and cooks in the tourist sector work extended days during peak season -- sometimes without any weekly rest

"Overwork is not a choice, it's a necessity, overtime is often a means of survival," according to financial daily Naftemporiki.

The current government has already legalised a six-day working week, especially during high demand in certain sectors, including tourism.