Four private hire taxi drivers have had their licences revoked or suspended by Oxford City Council after being caught illegally picking up passengers.

When private hire drivers pick up passengers without a booking, a practice known as plying for hire, their insurance automatically becomes invalid.

Hackney carriages are allowed to pick up passengers, but private hire drivers are only supposed to take bookings from their office.

Leader of the council Corinna Redman, who chairs the hackney carriages and private hire licensing committee, said: "The committee's primary concern is public safety.

"It is illegal for private hire drivers to ply for hire and it is certainly unacceptable for the public to be riding in a taxi that has invalid insurance.

"The committee has imposed the penalties to send a clear message to drivers to clean up their act, and to make sure that the public are aware of the danger.

"The council certainly values the work that private hire drivers perform and we are aware that at times in Oxford there is a wait for a hackney carriage, but the committee must act on complaints and enforce Government regulations."

The four private hire taxi drivers who have had their licenses suspended or revoked are not being named.