Animal welfare campaigners who secretly filmed a performing elephant being chained and hit with a pitchfork have condemned the "derisory" sentence given to a circus owner convicted of causing unnecessary suffering to the animal.

Bobby Roberts was also convicted of failing to prevent an employee from repeatedly beating 60-year-old Anne, an Asian elephant.

In addition, Roberts, 69, who ran Super Circus in Polebrook, Cambridgeshire, failed to ensure that Anne's needs were met by not giving her medication for her arthritis.

He was given a three-year conditional discharge at Northampton Crown Court but was not ordered to pay costs and was not banned from owning animals. His wife Moira, 75, was cleared of all three charges by District Judge David Chinnery following a five-day trial.

Following the hearing, Animal Defenders International (ADI), the organisation which covertly filmed the abuse over a three-week period, criticised the sentence. Spokeswoman Jan Creamer said: "Despite the considerable suffering caused to Anne the elephant, the sentencing meted out to Mr Roberts is derisory and provides no faith that the Animal Welfare Act can protect animals in circuses."

She went on: "People should be held responsible for the day-to-day experiences of their animals. If they don't have the staff or they don't have the people to look after their animals properly, then they shouldn't be keeping them."

Mrs Roberts wept as District Judge David Chinnery read out the verdicts on her and her husband. The court had been shown footage filmed covertly by ADI between January 21 and February 15 last year. It showed Anne constantly chained up in a barn at the circus's winter quarters by one foot and one hind leg and being struck repeatedly with a pitchfork by her groom.

Roberts told the court that he had no idea of the actions of the groom and that it was "disgusting and disgraceful" behaviour. He said if he had known, he would have fired the groom, who is believed to be back home in Romania.

Roberts also told the court that he was unaware that Anne had been constantly chained and that the groom had not followed his instructions to let the animal loose behind an electric fence in a cordoned-off area of the barn when possible.

Giving his verdict, District Judge Chinnery criticised ADI and the way campaigners had obtained the footage. He expressed concerns over the way the video was released to the media and that the Roberts had been "tried by the public, who have only the footage of the cruelty to the animal upon which to make a judgment".