The New Zealand Transport Agency (NZTA) is coming under fire for banning its staff from using Uber.
It has issued a directive to staff to stay away from the ride-sharing app, over fears that drivers might not have a P endorsement to carry passengers.
Since April, Uber has refused to comply with the law which states drivers must have a P endorsement, saying it costs too much.
But Matthew Rhodes from the Taxpayers' Union says the agency isn't considering the costs of a normal taxi fare.
"Government departments should be using the most effective, cost-effective means which is fit for purpose, wherever possible," he told RadioLIVE on Monday.
"I think any attempt from a Government agency to cut out these necessary expenses should be encouraged, not condemned."
Documents released to the Weekend Herald under the Official Information Act show NZTA staff have taken 56 Uber rides since January 2015.
"We know of drivers 'approved' by Uber who have variously been found by the agency in the past to be medically unfit to drive, have assault charges awaiting court hearings and so on," operational policy manager Richard O'Reilly wrote in an email to staff.
NZTA's group manager for access and use Celia Patrick says the agency does not want to stand in the way of innovation, and understands the Uber app is very popular and convenient.
But with the way Uber currently does background checks, she says NZTA cannot assure customers that all drivers are medically fit and have been properly vetted for criminal convictions.
"We cannot encourage New Zealanders, including our own staff, to use a service which in some cases is operating outside of the law," she told Newshub.
"New Zealand law requires that people driving for Uber or any passenger service hold a passenger endorsement.
"We have an obligation to ensure that people carrying passengers for a living have been properly vetted for criminal convictions, including any overseas convictions, risky health issues or other matters which could put the travelling public at risk."
Ms Patrick says NZTA is regularly advising prospective Uber drivers what is required of them to legally carry passengers, and explained the possible consequences of driving without an appropriate licence, which can include significant fines.
Mr Rhodes says if NZTA is serious about cracking down on Uber, it should do it through enforcing the law.
In response, NZTA says it has made 118 formal warnings, 141 infringement notices, and ordered 29 drivers off the road.
Mr Rhodes says since NZTA has not banned Uber, its employees should be encouraged to use the most cost-effective option to the taxpayer, he says.
"There are NZTA staff out there who are willing to cut their organisation's transport expenses by using Uber, but they're then denied by their superiors."
The Government has previously warned Uber it could be banned if it doesn't resume checking its drivers' backgrounds.
NZTA staff are allowed to use Uber "in their own time and with their own money".