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.

His amendment would exempt unions and labour organisations, as well as groups such as charities, non-governmental organisations, community groups, churches and sports bodies.

Five trade unions are affiliated to the Labour Party and donate to it, but Mr Chauvel said he had put in the amendment off his own bat. He said the unions were relaxed about the bill, but he believed they were in a similar position to philanthropic, voluntary organisations which were not-for-profit.

"When trade unions came up, it seemed to me that they fell on the not- quite-so-sinister-and-behind-the-scenes side of things."

He said corporate lobbying had the power to change policy, and was often done on the quiet.

"There is a big public interest in knowing what corporates are doing because they can afford heft lobbying and hospitality, and research and all the rest," Mr Chauvel said.

Ms Walker said changes were needed to ensure the bill did not cover everyone who spoke to an MP. However, she believed trade unions should be covered by the bill despite Labour's stance.

"It is important for transparency that if we are going to have a register of lobbyists that gives us a clear picture of where influence is taking place, then it needs to apply across the board. And that means it does need to capture not-for-profits, NGOs, trade unions ..."

Ms Walker said she wanted to receive public feedback and see what changes the select committee would make before deciding what amendments were needed.

Her bill has been referred to the government administration committee but submissions have not yet been called.

By Claire Trevett @CTrevettNZH Email Claire