The Retailers' Association is urging Labour MP Shane Jones to put his money where his mouth is and repeat his allegations about the Countdown supermarket chain outside Parliament.
Mr Jones last week used parliamentary privilege to accuse the supermarket chain of blackmail and anti-competitive behaviour.
On Tuesday, Parliament directed the Clerk of the House to release a letter from Mr Jones to the Commerce Commission requesting an investigation into allegations about Countdown.
ACT leader John Banks has suggested Shane Jones distribute a letter containing his accusations on the steps of Parliament, where he would not be covered by privilege.
Retailers Association chief executive John Albertson echoed that call saying it was inappropriate to keep sounding off on the matter when it has been referred to the Commerce Commission for investigation.
"If I'm going to criticise you in public then I should be prepared to put my money where my mouth is and make the statements accordingly. I think if somebody's got a point to make about any organisation they should be prepared to make the claims outside of the House rather than hiding behind privilege."
Mr Jones said parliamentary privilege allowed MPs to speak truth in the face of adversity, menace and threat.
"It enables parliamentarians to bring grievances that are of inordinate public interest to the attention of the general public without facing the crippling threat of legal destructive action."
Countdown rejects the allegations, and says the letter is unspecific.