Corrections Minister Judith Collins said the woman who's claiming she paid a prison guard $500 to smuggle a hundred grams of tobacco into Wiri Prison has implicated herself in a very serious crime.

The police are now investigating.

But Labour's Kelvin Davis said she shouldn't be shooting the messenger, she should be going after the guards.

"If a prison guard is doing this sort of thing it puts other prison guards in danger. That's one of the main reasons why this has to stop. We can't have some prison guards putting their co workers into jeopardy."

Mr Davis said he's spoken to the police about contraband being smuggled into the Serco prison at Wiri.

"This was 100 grams of tobacco for $500. I've heard of a packet of cigarettes going for $800. I've heard this from a number of sources so it is a commodity to be traded, it's currency in prison, that's why so many people want it."