Operation Debar was the biggest crackdown of its kind in the UK

The force said Operation Debar was the largest initiative of its kind in the UK.

In total, nearly 1,700 cars were seized and 133 arrests were made, as drivers without a licence or insurance and road tax dodgers were targeted.

The operation also involved the vehicle licence agency, the DVLA, and the Motor Insurer's Bureau.

Officers were equipped with automatic number plate recognition systems.

North Wales Police say a wide variety of offences were detected, including possession and supply of drugs, car theft, drink-driving, possession of offensive weapons, deception and fraud.

Illegal immigrants were also discovered.

In one incident, two men in a 4x4 car were arrested on suspicion of possessing Class A drugs and cannabis. During a search, �24,500 was seized and police inquiries are continuing.

People who don't pay tax or insurance are often involved in other forms of criminality Deputy Chief Constable Clive Wolfendale

During the operation, each of the 16 policing districts in north Wales was visited at least once by a team of officers using number plate reading cameras.

Computers instantly cross-checked details on tax and insurance databases.

The deputy chief constable of North Wales Police, Clive Wolfendale, hailed the success of the initiative.

"We've seized cars which haven't been taxed for a period of at least 8 weeks and are not insured. So this isn't for people who've just slipped up and haven't gone to the post office the next day," he said.

Police said other crimes were also detected in the car operation

"We've been targeting people who habitually misuse vehicles, don't have insurance, don't have tax and are defaulters. Let's remember that the people who don't pay tax or insurance make it more expensive for the rest of us."

The deputy chief constable stressed that a wide variety of non-motoring offences had been detected during Operation Debar.

"We do find that people who don't pay tax or insurance are often involved in other forms of criminality. it's been a great success, tackling criminality rather than the ordinary motorist."

"By targeting the vehicles we are effectively tackling the criminal fraternity and the resources they can call upon."