Police are investigating prison officers at Mt Eden and Wiri in south Auckland over allegations they've received money for smuggling in contraband.

In the case of Mt Eden there were apparently bank transfers and at Wiri a prisoner's family member met with an officer behind a petrol station and gave him tobacco for the prisoner in return for money.

Corrections Minister Judith Collins said the claims are being investigated - but acknowledges it does go on.

"Since 2007 there have been four corrections officers who have been jailed as a result of accepting bribes of this nature, bringing in contraband, and there are two that are currently before the courts, so it is treated extremely seriously.

Ms Collins said the woman who made the claims publicly is now deeply implicated.

"Unfortunately the person who's made the allegations has now given evidence, and it's been publicly available, that actually implicates her in a very serious offence."

In Parliament Ms Collins, who's minister of both Corrections and Police, was challenged by Labour's Kelvin Davis.

"How has she allowed SERCO guards at Wiri to allegedly smuggle contraband to prisoners on her watch," Mr Davis said.

Ms Collins replied: "If there's any allegations of bribery and corruption then that member should take them straight to Corrections or Police. If he's too scared to do so he should bring them to me."