Traffic police numbers across Britain have been cut by 12% in five years, with some forces suffering 30-40% reductions, according to new figures.
The number of traffic police in Scotland has gone up nearly 4% but numbers are down nearly 13% in England and by more than 31% in Wales, data released by road safety charity Brake and webuyanycar.com showed.
The two groups said the largest cuts have been in Bedfordshire, where road police have been reduced by nearly 44%, while in South Wales and Dyfed Powys there have been reductions of around 40%.
In West Mercia and Hampshire the reductions are more than a third.
Brake deputy chief executive Julie Townsend said: "It is desperately worrying such large cuts continue to be made to traffic policing, just as progress is being made to improve the law on deadly drug-driving.
"Roads police officers do a vital job enforcing important safety laws and protecting the public. Their work is proven to save lives and prevent injuries and suffering. Cutting traffic police is a false economy, because the crashes and casualties they help to prevent inflict such devastation and are a huge drain on public services."
She went on: "These cuts also undermine important progress being made by Government to tackle drug-driving - because as much as we need a new drug-driving law and screening devices, we also need the officers out there to enforce it.
"We urge the Government to make roads policing a national policing priority, to make sure we have a strong deterrent against the risk-taking on roads that can easily cost lives."
A spokesman from webuyanycar.com added: "It's imperative that the police have the resources to protect all road users from the drivers whose criminal behaviour puts us at unnecessary risk.
"We urge the Government to heed the warning of our report and stem the cuts before we witness a hike in needless incidents; incidents that, without road policing, are waiting to happen."