Frenchcompanies will be required to guarantee a "right to disconnect" to their employees from Sunday as the country seeks to tackle the modern-day scourge of compulsive out-of-hours email checking.

From January 1, a new employment law will enter into force that obliges organisations with more than 50 workers to start negotiations to define the rights of employees to ignore their smartphones.

Overuse of digital devices has been blamed for everything from burnout to sleeplessness as well as relationship problems, with many employees uncertain of when they can switch off.

The French measure is intended to tackle the so-called "always-on" work culture that has led to a surge in usually unpaid overtime - while also giving employees flexibility to work from outside the office.

"There's a real expectation that companies will seize on the 'right to disconnect' as a protective measure," said Xavier Zunigo, a French workplace expert, as a new survey on the subject was published in October.

"At the same time, workers don't want to lose the autonomy and flexibility that digital devices give them," added Mr Zunigo, who is an academic and director of research group Aristat.

The measure was introduced by Labour Minister Myriam El Khomri, who commissioned a report submitted in September 2015 which warned about the health impact of "info-obesity" which afflicts many workplaces.