People will be legally liable for the basic welfare of their pets under new laws coming into force in England.
The act has been labelled a bill of rights for pets
The Animal Welfare Act, which became law in Wales last week, includes harsher fines of up to £20,000 and jail terms of up to a year for cruelty.
The RSPCA is raising awareness of the act, which has been dubbed a bill of rights for pets, ahead of its official introduction on Friday.
The government says existing laws are outdated and too inflexible.
The Act, which raises penalties for cruelty from the previous maximum of six months in prison or a £5,000 fine, is the most significant new law on animal welfare for 94 years.
It imposes a duty of care for non-farm animals, for the first time.
THE NEW LAW
Welfare needs including proper diet and veterinary care must be met
Raises age for buying a pet from 12 to 16
Almost doubles max prison term for abuse from 6 months to 51 weeks
The duty of care includes making sure that animals have a proper diet, are housed with or apart from other animals according to their need, have the ability to express normal behaviour and are protected from pain, suffering, injury and disease.
Under the Act the minimum age for buying a pet will rise from 12 to 16, and under-16s will not be allowed to win a pet as a prize.
The Act also bans the docking of dogs' tails for cosmetic reasons, with the exception of "working" dogs used by the police, armed forces, search and rescue, and gun dogs.
Animal welfare minister Barry Gardiner said: "For the first time ever, there will be legislation to stop the suffering of pet animals before it occurs.
"By allowing early intervention this Act works on the principle that prevention is better than cure."
He said persistent offenders would be deterred by stronger penalties.
RSPCA director general Jackie Ballard said most people were well aware of their animals' needs, so the change in the law would not affect them or their pets.
But she advised anyone who was unsure about their pets' needs to contact the RSPCA or their vet.
The Federation of Companion Animal Societies said the government had not done enough to make pet owners aware of the legal change.
It was also concerned that not enough had been done to draft codes of practice that were intended to back up the Act.
Federation chairman Chris Newman said: "These codes are supposed to provide a defence for pet owners under the act, but they don't exist."
RSPCA vet David Grant said: "Animals need appropriate food and water, shelter and exercise, and to be treated quickly if they are sick or injured.
"Crucially now owners and keepers will have a legal responsibility to meet the basic welfare needs of their animals."
The RSPCA opposes performing animals in circuses and zoos and says that under the Act, further regulations dealing with issues such as circus animals may be introduced in the future.
A panel of experts appointed by the government to look at whether stricter regulations or a ban on circus animals is needed is due to report by the summer. Any changes would come into force by 2008.