There's renewed debate over whether an Independent Costings Watchdog is needed to verify election promises.

Labour, National and the Greens have all shown support for the idea.

The Taxpayers' Union's Jordan Williams says an office separated from the Government of the time is needed to verify each party's election promises for the sake of democracy.

"So we don't end up like the situation where we used to have, where even with the big parties, there was just no questioning of costs."

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