Hundreds of people have been caught drug-driving in the space of a month.
During December, 1,888 motorists across the UK were stopped and screened for drug use, with 931 testing positive.
A change in the law last spring meant it was the first time that police officers could carry out roadside screening for illegal substances or some legal medications over the festive period.
Nationally, fewer motorists were actually tested for drink-driving - 110,226 in December 2015 compared with 133,996 in 2014.
But the proportion who tested positive for drink-driving, refused to take the test or failed to give enough breath rose - it was 5% in 2015, up from 4.39% the previous year.
National Police Chiefs' Council lead for roads policing Chief Constable Suzette Davenport said: "These results show that new legislation and detection devices have helped us to keep the roads safe.
"Officers across the country, using their local knowledge and intelligence to focus on high-risk locations, are better equipped than ever to catch drivers who are under the influence of drink or drugs, even at very small amounts.
"Over the last Christmas, we detected and prosecuted more people than ever who have taken the very dangerous risk of driving after taking drugs."
RAC chief engineer David Bizley said it was "worrying" that so many drivers had been caught breaking the law, and claimed there may be more than figures suggest.
He said: "If a police officer suspects that a motorist is driving under the influence of both drink and drugs, they will normally test for alcohol only because this is far cheaper and simpler than testing for illegal drugs and the penalties are similar for both offences.
"The figures published by the police for positive drug tests are therefore likely to understate the number of motorists caught when driving under the influence of drugs."
Police in Wales said 498 drivers had tested positive, refused or failed during the same month, and a total of 99 motorists were arrested for drugs offences during the crackdown.
:: North Wales Police tested 8,894 people, with 82 positive, refused or failed. 35 drug arrests.
:: South Wales tested 4,409 with 205 positive, refused or failed. 26 drug arrests.
:: Gwent tested 1,130 with 47 positive, refused or failed. 21 drug arrests.
:: Dyfed-Powys tested 8,378 with 164 positive, refused or failed. 17 drug arrests.