More competition is needed to cut petrol prices - and somebody should petition Gull to expand, Transport and Energy Minister Simon Bridges says.
A leading competition expert has warned petrol companies co-ordinate prices, and that is likely to worsen when Z Energy takes over Caltex.
But Mr Bridges said the evidence showed there was "workable competition" in the market.
"But, like electricity a few years ago, would we benefit from more competition? We absolutely would.
"And someone should take a petition to Gull to get them moving even more around the country, because where they go, the prices fall."
Gull largely operates in the upper North Island.
The Commerce Commission has approved the buying of Caltex by Z Energy, a move that will see a single company supply about half the petrol stations.
That decision was not unanimous. Dr Jill Walker stated that the merger would likely entrench price co-ordination, and see it occur more completely and quickly.
Asked by Labour MP Stuart Nash about petrol prices in a select committee appearance yesterday, Mr Bridges said he respected the Commerce Commission's majority view that there was no evidence of price co-ordination.
AA spokesman Mark Stockdale said service stations followed or matched pricing. He agreed with Mr Bridges about the "Gull effect", and said motorists would benefit if the company expanded.
General manager of Gull New Zealand David Bodger said there were five sites in the consenting process, and more planned after that.
Bus lanes for Bridges
Transport Minister Simon Bridges will soon be able to zip down bus lanes - he is upgrading his personal vehicle to an electric SUV.
Mr Bridges will take possession of a Mitsubishi Outlander PHEV, priced from $60,000, next month. He revealed the change yesterday, after Labour MP Stuart Nash asked if he would recommend Crown cars be electric.
Mr Bridges said procurement rules would enable the Government and private companies to investigate the bulk purchase of electric vehicles.