The number of motorists charged with drug-driving in London has almost tripled over the past 12 months, according to new research.

Figures obtained by comparison site, using freedom of information data, reveal that the number of charges for drug-driving in London increased from 310 in 2014/15 to 1,209 in 2015/16. The research also revealed a 140% increase in drug drive charges across the UK during the same 12 month period.

The research also found that 15% of the drivers who admitted to drug driving had done so after taking legal drugs, such as codeine and hay fever medication. Two thirds of people who suffer with hay fever admitted that they would drive after taking antihistamines, despite the fact that the medication can cause drowsiness and reduced concentration.

The rise in drug driving arrests coincides with changes to drug-driving legislation, which came into effect in March 2015. The new law means that it is an offence to drive with any one of 17 specified legal and illegal drugs above a certain level.

Paula Porter, head of criminal law at Thompsons Solicitors, said: “These latest stats suggest that the drug driving legislation introduced last year has made a significant impact on traffic officers’ ability to police drug driving in the capital and UK-wide. However it is apparent that many drivers are still choosing to flout the law and risk the lives of others by driving under the influence of legal and illegal drugs.

“With over 15% of drivers admitting to driving while under the influence of legal drugs, and with hay fever season upon us, it is vital that drivers understand how their medication may affect their ability to drive.

“While the government must ensure police forces across the UK are properly funded and resourced to patrol the roads and apprehend reckless drivers, the government must also focus their attention on raising awareness of the too little known dangers of driving under the influence of over the counter and prescription drugs.”