More than half of chauffeurs work days averaging 11 hours or more, according to powerful new research that has led to calls for maximum shift lengths policed by HGV-style tachographs.

A survey carried out by general workers union GMB found nearly half of the 600 chauffeurs interviewed at Heathrow airport worked 70-hour weeks. Six out of 10 drivers also said they’d suffered some form of coercion from their employer to work more hours.

“The next Selby is going to be caused by a driver working for a licensed chauffeur or taxi company,” said GMB head organiser Martin Smith, referring to the deadly 2001 rail crash caused by a driver falling asleep at the wheel. “If we know the company has coerced that driver to work long hours, then we’ll prosecute to the full extent of the law.”

GMB and road safety charity Brake are calling for 48-hour weeks for professional drivers, and the fitment of tachos to monitor those hours. “This survey is extremely disturbing,” said Cathy Keeler, Brake’s head of campaigns. “The Government needs to tighten the law and provide effective enforcement to ensure employers do not put pressure on drivers to work horrendous shifts, putting themselves and other innocent road users in danger.”

However, the chauffeur companies aren’t so supportive, pointing out that their business thrives on flexibility. “A tachograph is clearly not an option for the service we provide,” said Doug Claringbold, operations director at Tristar, whose 450-strong limousine fleet includes the Volvos used to chauffeur Virgin Atlantic’s Upper Class customers. “We fit tracking units so we can monitor how long our chauffeurs are driving. It means we can enforce any new legislation with existing technology.”

The drivers themselves say low wages are to blame for long hours, not coercive bosses. “I’m under no pressure, but at £5.50 an hour you’ve got to work a lot of hours to get a living wage,” said Dave Singleton, a chauffeur driving a Volvo S80 for Tristar. “I aim to work 300 hours most months, but if the Government brings a maximum of 48 hours, then drivers won’t earn enough to live on.”

A recent prosecution saw a potato delivery company fined £30,000 plus costs after an employee crashed his van and died after working a string of 19-hour days.