Opposition parties have called for GPS data from Crown limousines to be released - a move which would reveal what speeds the vehicles had been travelling.
The Department of Internal Affairs (DIA) is also refusing to release details about any speeding tickets collected by ministers driving their taxpayer-funded cars, citing privacy reasons.
The secrecy has not impressed Labour, which said it appeared the Ministerial Services section had something to hide.
And this morning Green Party transport spokeswoman Julie Anne Genter also said speed information should be released.
"I don't see why they can't release the data on speeding, I don't see how it is protecting public interest.
"With National, we have seen that sometimes ministers think they are above the rules and regulations that apply to everyone else, like when Gerry Brownlee rushed through airport security."
GPS units have been installed in Government and council cars, and data from New Zealand Transport Agency (NZTA) and Auckland Transport vehicles was released to the Herald earlier this year.
NZTA data showed staff using work cars had broken the speed limit at least 8500 times in three months but had not been given any infringement notices.
Transport Minister Simon Bridges said at the time that the findings were "embarrassing" and "disappointing".
Now, the DIA's general manager of ministerial services, Andrew McConnell, has confirmed that Crown limos are equipped with GPS units but says the data will not released because it was "necessary to maintain the effective conduct of public affairs through the protection of such ministers from improper pressure or harassment".
Labour's transport spokesman, Phil Twyford, said it appeared the Ministerial Services section had something to hide.
"If NZTA has released their GPS data on speeding, I don't see why Government ministers can't. It is in the public interest. It's worth protecting GPS locations. But at first glance I can't see any downside to releasing the data that relates to speeding."
Acting Transport Minister Craig Foss said it was an issue for Ministerial Services.
The department did agree to release some details of speeding tickets collected by Crown limo drivers. Between January 2013 and July 2015, they were caught speeding 13 times.
The worst infringement was for a driver caught travelling 17km/h over the limit in a 50km/h zone.
Mr Twyford said the number of tickets was "not outrageous" given the size of the limo fleet and the kilometres travelled over that period.
It was not known where the speeding tickets were issued, which minister they related to, or whether the fines were paid or waived by police.
Mr McConnell said any infringement notices VIP Transport Services received were sent to the driver.
"The record is between the driver and police, with no involvement from the department," he said.
As well as Crown limousines for Wellington travel, ministers get "self-drive" cars to use in their electorates.
Internal Affairs withheld any information on speeding infringements related to these cars.
"I do not consider that the withholding of this information is outweighed by other considerations which render it desirable or in the public interest to make that information available," Mr McConnell said.
After the NZTA data was made public, Mr Bridges said: "To say I'm unimpressed would be one of my big understatements. I've directly contacted both the chair and chief executive on learning about this. I've made my views and expectations crystal clear. I've sought assurances from them both that ... speeding will come down. It is embarrassing."
In 2005, then Prime Minister Helen Clark's driver and three police were charged with reckless driving in relation to a motorcade that at times exceeded 150km/h.