Image caption About 5,000 owners a week already voluntarily choose to microchip their dogs

Compulsory microchips for dogs are to be introduced in England, under plans expected to be announced on Monday.

Ministers are expected to say that every newborn puppy should be microchipped to make it easier to trace and prosecute owners of violent dogs.

But critics of the plan question its effectiveness and the potential cost of the move.

Earlier this month Northern Ireland became the first part of the UK to introduce a law on microchipping.

The microchips each contain a unique number and are implanted into the loose skin between a dog's shoulder blades.

The information will reportedly be stored on a central database which can be accessed by the police and the RSPCA.

'Irresponsible owners'

Charities have broadly welcomed the rules, suggesting they could also help reunite lost dogs with owners.

A spokesman for the Department of Environment, Food and Rural Affairs said: "We will very shortly be announcing a package of measures to tackle the problems caused by irresponsible dog owners.

"This is an issue we take extremely seriously and so have taken the time necessary to get the policy right."

About 5,000 owners a week already voluntarily choose to microchip their dogs.

Welsh Environment Minister John Griffiths said last December that he was considering introducing legislation requiring all dogs in Wales to be microchipped.

The Welsh government is to consult on plans for compulsory microchipping later this year.

Meanwhile, Scotland's Cabinet Secretary for Rural Affairs and the Environment, Richard Lochhead, said in March there were no plans in Scotland to introduce compulsory microchipping.