Jacinda Ardern ruled out a capital gains tax while she's leader, but the Reserve Bank says tax of some form should be considered.

Speaking to Stuff today, Reserve Bank governor Adrian Orr said: "I'm aware the Government has said publicly they have ruled certain things off the table. They have ruled that off but ...we're going to have to speak openly, frankly and with integrity."  

It comes after Finance Minister Grant Robertson wrote a letter to Orr, asking for feedback on the bank can do to help with housing affordability. 

Deputy Reserve Bank Governor Geoff Bascand says housing is a complex and entails a wide set of issues.

He told Heather du Plessis-Allan the Bank's happy to contribute to the conversation.

"I expect it's going to take a number of different actions. There's no magic wand there." 

Asked if a CGT should be introduced, Bascand says that tax is an option, but it doesn't necessary solve the problems. 

"You look at tax from a lot of angles, of efficiency and equity, and that should be part of a package."

He says that if the Government wants to look at housing, then it needs to look at it from lots of angles and have a "constructive, mature conversation". 

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