The Bill, published yesterday, will ban pet shop owners and fairground operators from selling or giving live pets to children under 16, unless there is a responsible adult present.
Current law permits the sale of pets to over 12s, but Ben Bradshaw, the Animal Welfare minister, said 12 was "simply too young" for a child to appreciate the long-term implications of looking after a pet, .
In Scotland, fairgrounds face an outright ban on giving away live creatures as prizes, under devolved legislation. But Mr Bradshaw said this would be "too nannyish" to be extended to England and Wales. The Bill does not ban the use of animals in circuses, as some campaigners wanted it to.
"Once this legislation is enacted, our law will be worthy of our reputation as a nation of animal lovers," Mr Bradshaw said. "Anyone who is responsible for an animal will have to do all that is reasonable to meet the needs of their animal."
The Bill will raise the maximum penalty for causing unnecessary suffering to an animal to 51 weeks' imprisonment and a fine of £20,000, four times the present limit.
It was introduced to Parliament on a day when police arrested two teenagers in connection with the death of a dalmatian named Spot, who was found hanging from a tree at Cudworth, South Yorkshire. The Sun newspaper has offered a £5,000 reward for information leading to the killers.
The new Bill will supersede the 94-year-old Protection of Animals Act, and will combine 20 pieces of legislation. A new duty will be imposed on pet owners to take "reasonable steps" to ensure animals have a suitable environment and a suitable diet, are able to express their normal behaviour, and are free from pain, suffering, injury and disease. The mutilation of animals will also be banned, although there will be exemptions. This means that cropping dogs' ears will become illegal, but cropping their tails will not.
But it will not affect other childish practices, like collecting worms, or keeping spiders in matchboxes, because the Bill applies only to vertebrates. Farm animals and animals used in scientific experiments are covered by separate laws.
During 2004, the RSPCA inspectors checked more than a million animals and found that nearly 70,000, including 20,000 dogs, were not properly cared for.
Jackie Ballard, the former Liberal Democrat MP who is now the RSPCA's director general, said she welcomed the new Bill: "It will become the most far-reaching improvement to the welfare of animals for almost a century. The new welfare offence will for the first time protect thousands of animals from enduring serious ongoing neglect each year."
An RSPCA spokeswoman added: "We would like to see an entire ban on the tail docking of dogs, but hopefully Parliament will see fit to do that and amend the Bill accordingly. We would also like a ban on the use of all animals in circuses."
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