Note: This story was first published Sunday, March 25

The Government is spending a startling amount of money to get rid of overstayers in New Zealand, but few people are being deported and very little of that money is being recovered.

1 NEWS has revealed taxpayers spent $1.7 million last year on airfares and escorts to deport overstayers - more than in any of the last five years.

Overstayers must repay those costs to be allowed to reenter, but less than 10 per cent of that $1.7m was recovered last year.

Figures obtained by 1 NEWS also show there are more than 10,000 foreigners in the country unlawfully.

But Immigration New Zealand admits it's not actively looking for most them.

Eleven-thousand people landed, and never left again, putting them in a pool of foreigners now living here with no valid visa.

And the 82 Immigration staff dedicated to investigating overstayers are not actively looking for most of them.

"Part of the reason why we can't find them is we don't have up-to-date knowledge as to where they are and what they are doing. And there is ample work coming from the prison system and ample work in the ones that we do identify to keep us busy. Could we do more? Perhaps," said Peter Devoy of Immigration New Zealand.

The ones that are found and then deported, cost a fortune. Over the past five years, $7.46 million has been spent in flights and escorts to get them home.

"The cost of the deportation is registered as a debt against the person. So if the person wants to come back to New Zealand then that debt has to be satisfied before they can do so," Mr Devoy said.

And some do simply repay their debt and return to New Zealand.

These people are deep underground - Immigration lawyer Richard Small

A case three months ago saw an overstayer sent back to Zambia. The cost was $47,542 and more than $43,000 of that was for escorts.

Other cases released to 1 NEWS under the Official Information Act show similar spending.

"The airlines that we do work with often have their own security and their own systems in place around these types of people and the movement of them," Mr Devoy said.

"So we're very much having to work with them as opposed to dictate to them."

The department admits it often waits for information to come in before it acts, but says that is set to change.

From June, Immigration NZ and Police will share data, allowing police to tell in real time the immigration status of people they're dealing with on the beat.

Almost half of all overstayers here are from the Pacific Islands, followed by China and India.

Immigration lawyer Richard Small says there's no real research into the reasons that people have overstayed, "but these people are deep underground".

And Mr Small says sometimes the wrong people are targeted to get the stats down.

"There are people that are a risk, there are people that commit crimes. And then there're others that their only crime really is being here and supporting terminally ill family members. I don't think that that's a good use of money."