Intensive pig farming is being phased out but the price of pork would jump $2 a kilogram if it was immediately stopped, the New Zealand Pork Board said yesterday.

Chairman Chris Trengrove spelled out the cost of moving to completely free-range farms amid controversy over conditions for farmed pigs.

He said that half of New Zealand's pork industry was free-range, and that the board was working hard to phase out long-term use of sow stalls.

If the industry was to go free-range overnight, Mr Trengrove said, the cost would be an estimated 50c a kilo to the farmer, which would translate to at least $2 a kilo on the shelf.

A New Zealand Pork statement yesterday said: "Consumers need choice, like choosing between eggs, some people are happy to pay a premium for free-range. Consumers can ask questions about source of products - we would encourage them to do that."

The pig farm at the centre of the latest animal welfare controversy has identified itself to Government officials and will be investigated today.

Agriculture Minister David Carter had earlier asked animal rights campaigners to give up the name and location of the farm shown on TVNZ's Sunday programme.

The images showed pigs frothing at the mouth and unable to move inside their cages and aired on TVNZ's Sunday programme.

Mr Carter said the farm would be inspected by authorities.

"The television images were disturbing. It is essential we find out if this intensive pig farming operation is in breach of the Animal Welfare Act," Mr Carter said in a statement released this morning.

However, SAFE campaigner Hans Kriek said he would not be disclosing the information immediately.

When asked by if that was due to publicity, Mr Kriek said yes.

"I'm not going to give you all the details of our strategy, which is a very sound one," Mr Kriek said.

He said the group may as well send Mr Carter the addresses of all pig farms because the one showed on television is "average" and it does not break any laws.

"I've seen them slightly dirtier, I've seen them slightly cleaner. I've seen them slightly better, I've seen them slightly worse," Mr Kriek said.

Comedian Mike King, who was the face of the New Zealand Pork Industry Products, described the pigs as screaming in distress and the smell as "unbelievable".

"The only way to describe it was like watching prisoners who have been locked up in solitary confinement for so long that they've just gone nuts," Mr King said.

He said described seeing the corpse of pig who had been dead for some time and others that were incapacitated.

"They were chewing the bars and frothing at the mouth," Mr King said.

He said pigs were living in their own faeces and urine.

Mr King said some people had suggested he had an axe to grind after not having his contract renewed with the pork board but Mr King said that was not the case and he still supported free farm piggeries.

He said when he agreed to put his face to pig products, he had "no idea" and believed nothing like this could happen in New Zealand.

Asked if he had done any research before putting his name to the campaign, Mr King said he did not and he had "no excuses".

"I should have done the research and done it properly but that's the price I will have to pay and carry with me forever," Mr King said.

Asked if he supported the immediate naming of the pig farm, Mr King said that was up to SAFE.

Mr Kriek said information on the farm "will come out in the next few days" but did say that the pig farm shown on television was a big player in the industry.

He said everyone needed to take responsibility for the disturbing pictures that were shown on television.

Mr Kriek said if the public did not like what they saw in the pictures, then they should stop buying pork products.

He said the Ministry of Agriculture and Fisheries did not do random checks on farms and were reliant on complaints coming from the public.

"These farms are not open to the public, so who the hell is going to complain, the farmer? Of course not," Mr Kriek said.

MAF spokeswoman Lisa Gibbison confirmed the agency did not conduct random spot checks on farms and relied on complaints from the public.

Green Party animal welfare spokeswoman Sue Kedgley said she was "incredulous" that Mr Carter, as the chair of Parliament's Agriculture Select Committee for the last three years, would not know that sow crates are not widely used in New Zealand.

"His apparent lack of awareness of a widespread and controversial farming technique calls into question his ability to handle the Agricultural portfolio.

"Not only is this a simple issue of systematic animal cruelty, our whole reputation as a farming nation demands more informed leadership from the Minister than he's currently displaying," Ms Kedgley said.