The National Party is all but certain to support a Commerce Select Committee inquiry into the price of milk.
Labour and the Green parties have been pushing for the parliamentary investigation after the Commerce Commission last week ruled out conducting a full pricing inquiry, saying there is competition in the wholesale and retail markets.
Prime Minister John Key says there was widespread support at Cabinet on Monday for a select committee inquiry.
Mr Key says it is important consumers have confidence in the way prices are set.
The matter will go to the National Party caucus on Tuesday for the final stamp of approval before the Commerce Select Committee meets later this week.
The question now is how broad an inquiry could be.
Labour leader Phil Goff wants wide terms of reference, but Mr Key says he would be concerned if an inquiry cut across work being done by officials on raw milk pricing.