New Zealand First is accusing Prime Minister John Key of breaking an election promise to use the proceeds from partial state assets sales for hospitals, schools and roading.

Official documents from July 2014 through to June this year show New Zealand will fund its contribution to the newly established Asia Infrastructure Investment Bank from the Future Investment Fund, set up from the money made from the partial sales.

Photo: RNZ / Alexander Robertson

In a speech during the National Party's campaign launch in 2011, Mr Key said assets bought out of the fund would be "long-lived, here in New Zealand, and owned by the Crown on behalf of all taxpayers".

New Zealand First leader Winston Peters asked Mr Key in Parliament how he could reconcile the contribution with that statement "when the Government's contribution to the Chinese-led, offshore Asia Infrastructure Investment Bank, $140 million, is coming from his Future Investment Fund".

Mr Key replied New Zealand had long been a participant in putting capital into bodies such as this.

"And actually that's a very good thing to do because that collective capital will be used to build our infrastructure projects right across the Asia region actually of which New Zealand companies may well also get an opportunity to participate in.

"The capital is used to support those projects and one day it'll probably be returned to New Zealand taxpayers."

Mr Peters asked Mr Key why this money was not being used in the provincial regions of New Zealand, many of which were struggling.

Mr Key replied that the contribution "is an asset, held on the New Zealand balance sheet, that is at home".

Mr Peters later said Mr Key seemed to think he could get away with "saying any old thing".

"First of all, when they sold these public assets, they were meant to go to Mum and Dad Kiwi shareholders. That was a lie.

"Then second, they were to pay for hospitals, schools and roading. Again that was an exercise in deception."

Mr Peters said investing in an overseas bank did not comply with Mr Key's earlier statements.