Around two million drivers have been involved in an accident or a near miss while carelessly driving a vehicle with just one hand, according to data from the Department for Transport.
This is typically the case when people eat, drink, smoke, tinker with a sat nav or use a phone when driving.
A study carried out by the University of Leeds quantified this as it found that a person's reaction time increases by almost double (44 per cent) when eating behind the wheel.
This means that if an individual's reaction time was five seconds using both hands, while eating it would increase to just over seven seconds.
The figure is lower for drivers that take a sip from a drink behind the wheel. This only increases reaction times by a fifth (22 per cent). Researchers put this down to the added concentration to get food out of packaging.
"It is widely accepted that the distraction of talking on a hand-held mobile phone may increase accident risk - hence the introduction of legislation in the UK, said Professor Samantha Jamson at the University of Leeds.
"Other activities that involve taking one hand off the wheel, such as eating or drinking, may also cause distraction."