Drug testing of beneficiaries is turning up an extremely low number of results showing drug use - and a lot of missing information about the controversial policy.
Of the 8,001 beneficiaries sent for jobs requiring drug testing, only 22 tested positive to drug use or refused to take tests.
The low number of results has been greeted as a victory by Social Development Minister Paula Bennett, who says the policy is driving beneficiaries away from using drugs.
But her office admits it has no data to support the claim. The scheme began in July and followed employers' concerns about drug use among job applicants. About 40 per cent of jobs listed with Work and Income require beneficiaries to be tested for drug use.
Repeated failure can lead to benefits being stopped for those with no dependants, or cut in half for those with children.
Figures for the first 12 weeks of the scheme, released through the Official Information Act, does not show how many of the 8,001 people referred for jobs requiring drug testing were tested.
Ms Bennett's office said it did not hold the information and employers might choose only one of a number of applicants to go through testing.
In a letter, deputy chief executive of Work and Income Debbie Power said there was no information available showing how much the drug testing scheme cost.
There was also no information showing actual or estimated savings.
In a statement, Ms Bennett said: "It's great so few people failed tests in the first six months of this new policy, that's partly due to the strong signalling effect of this policy where many people reported quitting marijuana use before it was even implemented, but we're also giving people the opportunity get clean before they're tested."
Labour's social services spokeswoman Sue Moroney said information on the benefits and cost of the policy should have already been collected.
She also disputed Ms Bennett's claim the policy was scaring beneficiaries off drugs.
"The other way of looking at it is there's 8,000 people who are not using drugs at all who are being sent off for drug tests.
"The government assumes the worst of beneficiaries and has no data to back it up."