Postmen are delighted, but civil libertarians grumble that Britain's sprawling surveillance state now wants to track the nation's estimated 8 million dogs. Others complain that the insurance plan would impose a financial penalty on innocent pet owners — while criminals who own violent animals will simply shirk the law.

"This is yet more surveillance and continuous data-grabbing by government who want to have as much information on us as it can possibly have," said Dylan Sharpe, a campaigner with privacy rights group Big Brother Watch. Opposition lawmaker Nick Herbert said the proposal risked "penalizing millions of law-abiding dog owners with the blunt instrument of a dog tax."

The government's proposals are aimed at tackling the growing problem of aggressive canines being used to harass, attack and even kill. In a country where guns are tightly controlled and even carrying a kitchen knife can result in a prison sentence, animal rights experts and politicians say street thugs have turned to dangerous-looking dogs to cow their victims.

The Royal Society for the Prevention of Cruelty to Animals said the number of complaints about dog fights had soared 10-fold between 2004 and 2008, the last year for which figures were available. In 2009, London Deputy Mayor Kit Malthouse called for action on what he called "weapon dogs."

His opposition Conservative Party says hospital admissions and court cases relating to dangerous dogs have soared.

High profile dog attacks — including one on John-Paul Massey, a 4-year-old who was mauled to death by a pit bull at his grandmother's house in the northern England — have also kept the issue high on the media's agenda.

Home Office Secretary Alan Johnson said there was "no doubt that some people breed and keep dogs for the sole purpose of intimidating others."

"It is this sort of behavior that we will not tolerate; it is this sort of behavior that we are determined to stop," he said. In television appearances defending the proposals, he said microchipping would help trace the owners of dogs involved in attacks, while insurance would ensure that victims of dog attacks were properly compensated for any injuries.

His proposals were largely welcomed by animal welfare groups, including the RSPCA, which said it had long supported chipping — primarily as a means of reuniting lost pets with their owners.

She described the devices as "tiny microchips, about the size of a grain of rice, painlessly inserted into the back of the dog."

The chips are easily readable by scanners used by dog wardens and veterinarians.

Postal workers and telecom engineers also cheered the proposals, with the Communication Workers Union saying many of its members "are regularly bitten by dogs that have been either left unattended or are simply not under control."

Caroline Kisko, of Britain's Kennel Club, said previous legislation had proven ineffective at controlling the country's dangerous dogs — and expressed the hope that any new rules would put a greater emphasis on animal welfare.

Still it was unclear when — or even if — Johnson's plans could become law. The proposals must undergo a consultation period — typically 12 weeks — which means they're unlikely to reach Parliament before Britain's general election, which must be called by June 3.

A host of European countries — including Norway, Switzerland, Austria, Croatia, Italy and Portugal — have introduced mandatory microchipping rules in the past few years, with nary a raised eyebrow. France requires that some breeds either be chipped or tattooed. Even in countries where the practice isn't required, cities such as Berlin and Prague demand that dog owners chip their pets.

Mandatory dog insurance, regardless of the breed, is already in place in parts of Germany and Switzerland.

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Associated Press Writers from across Europe contributed to this story.