More than 160 people have been fined in Devon and Cornwall since new penalties for using hand-held mobile phones while driving came into force last month.
Police said they were surprised and disappointed that so many people were still flouting the law.
At least 164 drivers in Devon and Cornwall have been fined £60 and had three points added to their licence.
Acting Ch Insp Richard Price, head of Cornwall's traffic division, warned that police were staying vigilant.
Collision warning
He said: "These figures are not what we expected. Quite clearly the message is not getting through.
"I really want to remind motorists that if we see you holding a mobile phone while you are driving you can expect to get stopped and get a fixed penalty ticket.
"You will get three points on your licence and a £60 fine at best.
"At worst, you could be involved in a very serious collision."