Motorists caught using a mobile phone while driving are set to face tougher punishments.

Penalty points will rise from three to four and fines will go up 50% to £150 under government proposals.

But the Institute of Advanced Motorists (IAM) warned that the move would not have a 'dramatic impact' unless there were more traffic police officers to enforce the law.

Under the measures, drivers of larger vehicles such as lorries would receive six points – up from three – for being caught on a hand-held phone because the consequences of an accident can be much more severe.

Drivers can be banned from the road if they receive 12 points within three years.

In 2014 using a mobile phone was a contributing factor in 21 fatal accidents and 84 serious ones, according to Department for Transport (DfT) statistics for Britain.

Neil Greig, IAM director of policy and research, praised the government's desire to improve road safety but added: 'What we need is an increase in traffic police officers who enforce tougher regulations, in which motorists would fear using a mobile phone at the wheel because they'll get caught, as opposed to just getting higher fines.'

RAC analysis of Ministry of Justice data showed prosecutions for the offence were down by almost half in five years, despite a study showing the practice is more common.

Just 17,414 prosecutions for drivers using their phone at the wheel were launched in magistrates' courts in England and Wales last year, down by 47% from 32,571 in 2009. But a 2014 DfT study found 1.6% of drivers in England were observed using a mobile, up from 1.4% in 2009.