The Labour Party wants to exempt trade unions from a bill to regulate lobbyists, saying unions are "less sinister" than professional lobbyists and corporates.
Labour MP Charles Chauvel has proposed an amendment that will exempt unions from Green MP Holly Walker's Lobbying Disclosure Bill, which passed its first reading almost unanimously last week.
The bill would require lobbyists to go on to a register, disclose which politicians they meet and sign up to a code of ethics to be written by the Auditor-General.
The bill would cover anybody paid to lobby MPs, whether it was for an organisation such as Greenpeace or a trade union, a company such as SkyCity or as a professional lobbyist.
However, Mr Chauvel said it was too broad and the exemption was being sought because Labour believed it should apply only to groups or people who lobbied for a commercial purpose rather than not-for-profit groups.