First it was school dinners, then chickens and, most recently, the people of Rotherham. Now Jamie Oliver is switching his campaigning zeal to a new subject: pigs, reports The Independent.

Oliver, whose Ministry of Food cookery show based in the South Yorkshire town is currently on television, will launch a campaign to improve the welfare of the UK's nine million pigs in January. Channel 4 hopes fellow chefs Hugh Fearnley-Whittingstall and Gordon Ramsay will join the campaign.

The show, which will form part of a new C4 food season, is expected to focus on the difference between British welfare standards and those on the continent, which produces half of the UK's pork.

The animal welfare groups the RSPCA and Compassion in World Farming welcomed Oliver's involvement, which they hope will shed new light on a little-investigated area of British farming, and spur free-range sales.

Oliver won his high profile with his personal missions to improve school dinners and conditions for broiler chickens. His show, Jamie's Fowl Dinners, sought to uncover the reality of intensive poultry production and featured the live slaughter of chickens. The same week, a three-part series by Fearnley-Whittingstall, Hugh's Chicken Run, also investigated intensive poultry production.

After the shows, horrified shoppers swept the shelves bare of free-range chicken and retailers announced they were doubling their orders for higher-welfare birds.

Oliver is expected to take a similarly uncompromising position in his new show. One of the areas he may look at is the Continental practice of castrating pigs without using any anaesthetic.

Pigs are considered to be one of the most pressing animal welfare problems by campaigners because they are considered to be the most intensively kept, after chickens. Standards are higher in the UK than in some countries, but campaigners say many pigs here face a cramped and unnatural life in barren units.

Pigs on the Continent are subjected to practices illegal here, such as sow stalls, and castration, which is legal here but not widely practised.

Channel 4, which is keen to emulate the success of the first Food Season 4, confirmed the existence of the new project and said details would be announced in a fortnight. "The chicken programme made quite an impact," said a spokeswoman.

Oliver's press chief, Peter Berry, said it was too early to discuss the show. The RSPCA said it was thrilled that the show would bring the issue of pig farming to a wider audience. Julia Wrathall, the RSPCA's head of the farm animals group, said that conditions for British pigs were 'very variable'. She added, "There are quite a number of pigs that have very good conditions that but those in small barren pens with no bedding are in conditions that are unacceptable."

The RSPCA is concerned that consumers are confused by terms such as 'outdoor-bred' when only the mothers of the pigs providing the meat have been kept outdoors. 'Outdoor-reared' is higher welfare than 'outdoor-bred' but not necessarily free-range.

Several million pigs are bred every year in the UK. About 40 per cent of sows are kept outdoors. Most of the fattening pigs, which end up as bacon or ham, are kept indoors. Some indoor systems are considered good, but at least 35 per cent are considered very poor.

Peter Stevenson, chief policy adviser of Compassion in World Farming (CIWF), said scientific research showed pigs were the most intelligent farm animals, as clever as dogs, but were often unable to express their natural behaviour in intensive farming. Many had no 'environmental enrichment' such as toys nor adequate bedding and had nothing to do. "Pigs suffer from really awful problems and are kept in utterly inhumane systems," he added. "Anybody who kept a dog in those conditions would be prosecuted."

CIWF advises shoppers not to buy pork with the Red Tractor mark, the industry's basic quality standard. The National Pig Association declined to comment, concludes The Independent report.