Key Points:

A long-serving Corrections officer at Auckland Prison has been arrested after a "sizeable amount" of drugs was found in his car as he arrived at work.

The man, in his mid-40s, was searched after department intelligence had led to suspicions about his behaviour.

"It was a planned vehicle search. He was coming in for his shift [on Friday], and Corrections staff detained him," said northern regional manager Warren Cummins.

Staff called the police after they found contraband in his car at the Paremoremo prison. "He was arrested for the possession of contraband items," Mr Cummins said.

Asked if the employee might have been trying to smuggle contraband for years, Mr Cummins said: "We will probably never know the answer. It could have been a one-off, it could have been ongoing for some time. [But] he did it on Friday and was discovered in the act."

Corrections' acting assistant general manager of operations, Karen Urwin, confirmed that drugs were found in the vehicle. She said this showed that the drive to stamp out criminal activities within the country's prisons was working.

The man is due to appear in the North Shore District Court this week. It is understood he plans to defend the charges.

The arrest comes as prison management has been under pressure to expose corruption and deal with it.

In November, the department began an inquiry into Rimutaka Prison, which chief executive Barry Matthews said had an unhealthy culture that had allowed corruption to fester.

The inquiry is in its final weeks and several officers have been suspended since it started, including Wellington Prisons regional manager Dave East.

Mr Matthews said in March that all prison bosses had been told to do some "sniffing around" amid signs that corruption was not unique to Rimutaka.

He has always maintained that most prison staff do an honest and professional job.

The department is also moving to have a single entry point at each jail, and aims to introduce legislation this year to make it an offence for anyone - staff or inmates - to have contraband in their possession within a prison.

Mr Cummins said Paremoremo had cracked down on drugs and only 13 per cent of random drug checks on inmates were positive in the past year - lower than the target of 15 per cent.

The maximum-security unit is known as a difficult site to smuggle contraband into. Successful attempts often involve staff, including contractors and prison officers.

Staff, like visitors, are routinely subjected to searches as they arrive at the prison.

There are no other investigations into contraband-smuggling at Paremoremo at present.

In May, four staff at the prison were suspended for allegedly using two inmates on an escorted work outing to work on their private homes. Further claims were made of improper use of the prison garage, where inmates allegedly accepted food and other bribes for working on private cars.

Allegations were also made that the garage was used to refit an officer's 11m yacht, but Corrections Minister Damien O'Connor said the boat in question was a "barely seaworthy 13-foot plywood dinghy being repaired ... for use by local Sea Scouts".

National Party corrections spokesman Simon Power said Friday's arrest showed that corruption was an ongoing problem.

"Six months ago Barry Matthews and the Corrections Minister were telling the public that corruption in our prisons was limited to a few bad apples. The problem is, these bad apples keep turning up.

"If there's no problem with corruption, I'm still at a loss why they would form an anti-corruption unit at headquarters."