A Bradford police chief has warned airgun owners to obey a new law or face a lengthy prison sentence.

Owners of a particular type of airgun must now have a firearms certificate or surrender the weapon to police. Otherwise they could face at least five years in jail.

From yesterday, it became an offence to manufacture, sell, purchase, transfer or acquire any air weapon that uses a self-contained gas cartridge system.

The weapons - often known as Brococks after the leading manufacturer - are easily convertible to fire bullets rather than pellets.

They were used in more than 80 serious crimes nationally, - including murder - between 2001 and 2002, prompting the Government crackdown.

An adapted Brocock was used to murder Bradford taxi driver Mohammed Basharat in October 2001. A gunman walked into his office at Little Horton Private Hire and shot the 33-year-old in the head.

He then fired two more shots into him as he lay dying on the floor. The killing was thought to be retribution for a road rage incident the previous day when Mr Basharat's cab had clipped the wing mirror of a hired Renault Clio, prompting the driver to threaten to kill him.

Today, Detective Super-intendent Phil Sedgwick, of Bradford North CID, said there had been a spate of crimes using the self-contained air cartridge guns in the Bradford and Keighley district around 18 months ago and he welcomed the new legislation.

"These guns can be converted to fire projectiles so anything that makes it more difficult for guns to be used in this way is good," he said.

"Five years in prison is a severe punishment and that is how it should be.

"Anything that punishes crime and prevents the use of guns has to be a good thing. I can't see any reason why anyone would need such a gun, unless it was for sporting use.

"If you have a gun like this you take serious risks, whether it is real or imitation. You could be confronted by armed police and you risk going to jail and being missing from society for a number of years.

"My message is to hand in your gun or action will be taken against you."

Richard Stubbs, deputy firearms liaison manager for West Yorkshire Police, said the legislation was tough but necessary. But he stressed that it only applied to self-contained air cartridge weapons, not all airguns, and said his department had been flooded with calls from people unsure of whether the law applied to them.

He said: "They are easily convertible but they are also capable of being fired without being converted.

"These guns are now prohibited and the clear message is hand them in as quickly as possible."

The new measures come under the Anti-Social Behaviour Act 2003.