Police are carrying out surveillance operations on motorists from the top of double-decker buses in attempts to clamp down on mobile-phone use at the wheel, as it emerged prosecutions for the offence plummeted by nearly 50 per cent.

West Yorkshire police is employing the new tactic as figures showed the number of traffic officers in England and Wales had also fallen by almost a third from 3,766 to 2,643 since 2007.

The cut in resources has had an effect on the number of drivers convicted of using a mobile a the wheel, the RAC said, which has almost halved to just under 12,000 between 2012 and 2016 according to figures from the Ministry of Defence.

According to the BBC Inside Out Yorkshire and Lincolnshire current affairs programme, officers have been placed on double-deckers to catch drivers using their phone at the wheel.

The strategy has resulted in officers identifying motorists illegally armed with their devices but the high volume of sightings has meant investigators are unable to record some offenders details quickly enough, according to the programme.

The cash-strapped force, which trialled the initiative last year, has even appealed for the public’s help to bring prosecutions - by asking regular bus passengers on the upper deck to video motorists that they see offending.