It is understood Prime Minister John Key is seeking advice from the Cabinet Office on the issue after saying yesterday he was not aware of rules prohibiting the use of officials for party policy reasons.
He said he believed Mr Bridges acted appropriately.
"You're allowed to use resources of the officials in terms of what would be Government policy."
However, last month Finance Minister Bill English said in Parliament that he had not sought costings on the bridges from Treasury because it was "a proposal by a political party" and to do so would be against the rules. Yesterday Mr Peters said it was a clear breach by Mr Bridges "and Mr English has dropped him in it".
The officials who provided the information could also be in the gun. The State Services Commission said it was talking to the NZTA to see if it breached strict rules that apply to public servants around requests for costings of party policies. Under those rules, requests for costings of party policies must come directly from the Finance Minister or the minister concerned. Officials must refer any such requests to the Minister of Finance and there are limits on the information they can provide and how it is handled. A spokesman for Mr English said his office was not notified of the request for information and costings on the bridges.
A State Services Commission spokesman said guidelines were sent out before general elections but the principles applied at all other times. "Following standard practice, SSC is discussing this issue with the agency concerned to better understand what occurred in this case."
He said ministers did have the right to govern during elections and byelections and were able to ask agencies for information.
"Agencies are obliged to provide the information requested."
Mr Little said rules existed so the incumbent governing party did not have an unfair advantage in election campaigns and he would sack any minister in the same position.
The Cabinet rule:
"Before and after an election, the incumbent ministers should ensure that any requests they make for advice or information from their officials is for the purposes of their portfolio responsibilities and not for party political purposes."
Information requested by Transport Minister Simon Bridges:
• March 5 and 6, 2015: NZTA sends three emails with information about one-way bridges in Northland and cost estimates.
• March 9: National's Northland candidate Mark Osborne announces promise to upgrade 10 one-way bridges.
