New legislation comes into force this week that will overhaul laws designed to protect animals, which have not changed for nearly 100 years.

From Friday, the Animal Welfare Act makes it a legal requirement for pet owners to do what is reasonable to provide for their animal's needs.

One aspect of the law is designed to stop pets becoming obese - and owners who fail to comply could be hauled through the courts.

Simon Barrett finds out what the act means for pet owners in Sussex.

EARLIER this year, two brothers were prosecuted by the RSPCA after their pet labrador's weight ballooned to more than 11st.

Magistrates convicted Derek Benton, 62 and his brother David, 53, of causing unnecessary suffering to Rusty after a £12,000 two-day trial in Ely, Cambridgeshire.

But they decided that Rusty - who was 11st 7lbs at his heaviest - could be returned to the Bentons providing it was properly cared for, and imposed a conditional discharge on each of the men.

David Benton, a crane driver, said afterwards that the RSPCA was behaving like "the fat police" and that he had been "dumbfounded" by the prosecution.

He said the dog was overweight because it suffered from severe arthritis and had a long-standing hip complaint so was unable to exercise.

Cases like the Bentons' could become more frequent when the Animal Welfare Act comes into force in England on Friday.

It includes a new welfare offence, designed to protect thousands of animals from enduring serious ongoing neglect each year, by legally obliging owners to care for their pets properly.

An RSPCA spokeswoman said: "Animals need appropriate sustenance, shelter and exercise, and to be treated 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. Obese pets are not a huge problem, it is more likely to be malnourished animals that we deal with.

"However the new law will give our inspectors much greater powers of intervention. Currently if an animal is being mistreated or not cared for properly we have to wait until it is suffering before prosecuting.

"But under the new law we will be able to give pet owners deadlines by which to comply with an order, or they will face prosecution."

She said the majority of pet owners will not need to change the way they care for their animals to comply with the new law - as most people already provide for their pet's needs. But the new law will help to tackle cases of ongoing neglect.

Cats Protection, a charity based in Haywards Heath, rehomes around 60,000 stray or unwanted cats and kittens in the UK each year. It has been involved in bringing about a change in the animal welfare laws.

Dominic Sullivan, head of legal services for Cats Protection, said: "These new laws represent the biggest change in animal welfare law for nearly a 100 years.

"As a charity that cares passionately about the health and well-being of the nation's favourite pet, we hope that the act will help to reduce feline suffering and ensure adequate punishment for those who abuse cats and other animals."

As well as increasing the penalties for those who inflict the most serious offences, the Animal Welfare Act makes it a legal requirement for pet owners to do what is reasonable to provide for their animal's needs.

These are a proper diet; somewhere suitable to live; any need to be housed with or apart from other animals; allowing them to express normal behaviour; and protection from pain, suffering, injury and disease.

Despite the new laws being welcomed by animal charities, some say an increase in expensive trials in cases such as the Bentons' would be a waste of time and money.

During the final debate before the Animal Welfare Act became law, Ben Bradshaw, secretary for the environment, food and rural affairs, said: "It is not the Government's intention to punish the owners of fat cats, although overfeeding an animal can be problematic."

Ernest Vine, of pressure group known as the Self Help Group for Farmers, Pet Owners and Others experiencing difficulties with the RSPCA, said: "We hope the RSPCA will comply with the intentions of parliament and will never again bring a case involving an overweight animal before the courts.

"Rusty was suffering in the care of the Bentons. Rusty has been suffering in the care of the RSPCA. And Rusty will continue to suffer until the day he dies, irrespective of whose care he is in.

"Most of Rusty's weight gain occurred following an operation to neuter him. Neutered or spayed dogs need 30 per cent less food than unaltered dogs and it is this factor that is contributing to so much obesity in the canine world."

Any pet owners who are unsure of what their animal needs in terms of diet, appropriate housing, exercise, company, and veterinary care, can contact the RSPCA on 0870 3335999 or call their vet for advice.