Parliament has directed the Clerk of the House to release a letter from Labour MP Shane Jones to the Commerce Commission, requesting an investigation into allegations about the Countdown supermarket chain.
Last week, under parliamentary privilege, Mr Jones accused Countdown of standover tactics towards suppliers, and of demanding retrospective cash payments to make up for lost profits.
He also tabled his letter to the Commerce Commission, but in a rare move, the Clerk of the House blocked its release because of possible legal action.
On Tuesday afternoon New Zealand First leader Winston Peters moved a motion directing the Clerk to release the letter.
That was passed by Parliament, after Mr Jones sought an assurance from the Speaker it would be covered by parliamentary privilege.
Mr Jones says since raising the matter in Parliament he's been contacted by dozens of supermarket suppliers backing up his claims.
Commerce Minister Craig Foss told the House any complaint to the commission about supermarket behaviour would be treated in confidence.
Countdown says it's disappointed that Parliament has released the letter containing what it says are serious and unsubstantiated allegations.
Countdown rejects the allegations, and says the letter is unspecific.
It says it's deeply disappointed that its team on the frontline has been impacted by what it calls broad and unsubstantiated accusations.