The Automobile Association says people who are high on drugs while driving are slipping through police checkpoints.
Legislation to address drug-driving was introduced in November last year.
As of 25 May, police say 183 people believed to be under the influence of drugs have undergone a roadside impairment test. Some 101 people have subsequently been charged with drug-driving after undergoing a blood test.
The Automobile Association's motoring affairs general manager, Mike Noon, says the drug-driving legislation is flawed and people are getting through checkpoints.
"It's only the grossly impaired that are being put through that test, so these are people who are very obviously affected by drugs.
"The AA is very concerned that there's a lot of people who won't be picked up for having drugs who will be involved in having accidents and crashes."
Mr Noon says the Government needs to introduce random roadside drug testing.
A drug education company also believes the current drug-driving laws are not adequate.
Methcon director Mike Sabin told Checkpoint on Monday the small number of impairment tests do not act as much of a deterrent and random roadside testing is needed.
However, Transport Minister Steven Joyce believes the new drug-driving legislation is working well.
Mr Joyce says the number of charges show police now have the tools to take drugged drivers off New Zealand's road, thus improving road safety.