There'll be more attempts to corrupt officers as the influx of deported Australian gang members influence organised crime in this country, a police gang expert says.

There's been a 26 percent increase in gang membership in two years, the largest growth since the 1970s.

The head of the national motorcycle gang intelligence unit, Detective Sergeant Ray Sunkel, said this was partly fuelled by the deportees from across the Tasman bringing with them a more sophisticated, social media-savvy approach which was bolstering recruitment.

Mr Sunkel said the deported Australian gang members - known as the 501s - have completely changed how the gang ecosystem in New Zealand operated.

He said while they were more likely to be armed, and to use violence, that was not what worried him the most.

"The single biggest fear I have ... the single biggest risk posed by the 501s is not guns and it's not drugs, it's corruption - it's our biggest risk."

He said the 501s know that for organised crime to truly thrive they need corrupt officials.

"As they come in to New Zealand, as they peddle their wares and their way of conducting organised crime business I expect that they will try to corrupt more."

Mr Sunkel said officers might not even be aware they were being sounded out.

"Yeah, I think an offer to head down the dark road often happens without people even knowing it, they don't even understand that they're being groomed.

"It's a gradual process to get someone who's not a corrupt officer - to corrupt them."

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Transparency International ranks New Zealand as the second least corrupt country in the world.

Police Association president Chris Cahill said one of the factors for the low level of corruption in New Zealand was that police were comparatively well remunerated.

"We're lucky in New Zealand, we know that one of the key things to stop corruption is to have a well paid police force and to have a good superannuation scheme.

"And New Zealand police have a compulsory superannuation scheme."

But police financial intelligence expert, Detective Superintendent Iain Chapman, said our low corruption ranking could be overstated.

He said the white collar professionals that worked for gangs were acting corruptly.

"Every time a lawyer and accountant or real estate agent or high-value dealer chooses to be part of an organised crime group that's corruption.

"Every time an importation [of drugs] makes its way into New Zealand, there are corrupt officials enabling that to happen.

"This is a process that is happening every single day."

Police assistant commissioner for serious and organised crime, Richard Chambers, said he welcomed the discussion about corruption because it would help officers recognise it if they were ever approached.