The Electoral Commission says it is going to report the Employers and Manufacturers Association (EMA) to the police for breaching a section of the Electoral Finance Act.
In a notice posted on its website last night, the commission said the EMA put adverts in newspapers on July 24 raising objections to proposed changes to the Kiwisaver legislation.
The adverts said "tell our politicians it is the wrong call" and listed MPs' phone numbers, the commission said.
It has decided the messages amounted to election advertising, and the EMA does not have registration as a third party - an organisation which is not a political party - which would allow it to take part in the campaign.
"The facts will be reported to the police," the commission said.
The EMA is not the first organisation to be reported to the police for contravening provisions of the controversial Act, which opposition parties say is hopelessly vague and badly drafted.
Earlier this year the Labour Party was found to be in breach of it, and Tui has been warned some of its Yeah Right! billboards contravene it.
Another victim was the Progressive Party, led by senior cabinet minister Jim Anderton, which was reported to the police earlier this month for running adverts advising people about the new law that bans BZP in party pills.