The government is not enforcing its own laws on the welfare of pigs, according to two animal lobby groups.
Save Animals from Exploitation (SAFE) and the New Zealand Animal Law Association, have filed a writ in the High Court in Wellington saying the use of farrowing crates and mating crates breached the Animal Welfare Act 1999.
Farrowing crates are used for the sow for several days before giving birth and for a week to ten days after birth of her piglets.
Mating crates are used when a sow is in heat.
SAFE ambassador Hans Kriek said both were cruel.
He said the court should tell the government to enforce its own laws, because the use of these crates did not allow the animal to express its normal behaviour.
"The crates confine a mother pig for up to three months a year," he said.
"This means that for three months the mother pig cannot even turn around - it is very tight for the animal to live like this and it is extremely cruel."
He added this was contrary to animal welfare legislation.
"All we want is for a judge to say to the government, 'Enforce your own laws'."
Minister of Agriculture Damien O'Connor said this very matter was being considered at present by the Primary Production Select Committee, and he would consider and act on any recommendations when that evidence was gathered and presented.
He also pointed out that a report in 2016 from the National Animal Advisory Committee (NAWAC) found farrowing crates provided the best balance between sow and piglet welfare, and there were problems with alternatives to farrowing crates.
The chairman of New Zealand Pork, Eric Roy said he was surprised that SAFE had gone to court when their own petition to the select committee was still being considered.
Perhaps they were seeking two bites of the cherry, he said, or perhaps, they were worried they would lose their argument.
Mr Roy said letting piglets that roam free after birth had higher mortality rates than keeping them with their mother in a crate.
The NAWAC report said farrowing crates were best on balance, because young piglets roaming free were "more susceptible to starvation, chilling or being crushed by the sow."