More than half of motorists tested as part of a drug-driving crackdown failed the screening, according to police data.
Throughout June and July police forces in England and Wales carried out roadside tests for both drink- and drug-driving and 57 per cent of those tested for drugs were found to be under the influence of banned substances – up on the previous year.
A total of 1,962 people were tested for the presence of drugs in the month-long programme, with 1,118 failing the checks.
In a similar crackdown last year, 2,022 people were tested, with 1,084 – or 54 per cent – failing while the failure rate in 2016 was 40 per cent, according to the National Police Chiefsâ€™ Council.
In comparison, 36,674 drivers were breathalysed to check for drink-driving offenders between June 14 and July 15. Around one in 10 – 3,667 – were found to be over the legal limit or refused to give a sample.
Officers can check for the presence of cocaine or cannabis using so-called â€œdrugalyserâ€ mouth swabs at the roadside while blood tests performed at a police station can be used to check for heroin and ecstasy.
Such test have been carried out across England and Wales since 2015 and will be introduced in Scotland in 2019.
NPCC lead for roads policing Chief Constable Anthony Bangham said: “Driving under the influence of drink or drugs is an incredibly dangerous and selfish decision to take, and it can have devastating consequences on people’s lives.
“Far too many people still attempt to drive after taking drugs and we are better prepared to catch them than ever before. We will ensure that they face the full penalty of the law.
“Our message is the same all year round: do not do it.”