She said a prisoner had to pay "rent" to the gangs and could earn it at the cards table.
"In order to pay that rent, they gamble to win it," she said.
"If they don't win the rent, and a lot don't, then they have to go to a family member outside prison to pay the rent or smuggle in contraband. It's actually being used as a vehicle for extortion and for perpetuating gang crime and potentially recidivism.
"This money is owed. If it's not paid within a very short period of time, it doubles, and it doubles again and it doubles again.
"So we will come in and have prisoners refer themselves to us and say, 'I have a problem with gambling. I never had a problem with gambling before I came to prison but I've got one now.'"
Ms Siegel-Woodward, who is based in Christchurch, said prisoners were not allowed to have TAB accounts and the TAB shut them down when they were discovered.
"We have asked them to investigate on more than one occasion. They have investigated, looking into the accounts to make sure they are not owned by prisoners," she said.
She said the Corrections Department and Care NZ, which run drug treatment units in eight prisons, also cracked down on the practice when it was found.
"In the Christchurch drug treatment unit they are not allowed to be in each other's cells and there is no card playing allowed. In all units, Corrections has prohibited access to the racing channel," she said.
A 1999 survey found that 16 per cent of men and 21 per cent of women in NZ jails were current "probable pathological gamblers", compared with 0.4 per cent of all NZ men and 0.5 per cent of all NZ women at the time.
Ms Siegel-Woodward said the adrenaline rush that many offenders got from gambling was identical to the excitement they experienced in planning and committing a crime such as burglary.
"Risk-taking is the link between gambling and committing crime," she said. "Once we were able to deal with the risk-taking, both were able to be addressed."
Corrections Department Deputy National Commissioner Rachel Leota said money was not available in prisons and gambling was prohibited.
"Staff look out for unauthorised items, including excessive amounts of food items available through the weekly canteen or a high number of phone cards, which may indicate gambling activity," she said.
"Prisoners who are found to threaten or coerce other prisoners are held to account."