Mana Party leader Hone Harawira risks a fine of up to $40,000 for a newspaper advertisement urging voters to "Vote 4 Hone" published without a promoter statement during the Te Tai Tokerau byelection.

The advertisement ran in the Northern Advocate on June 24 - the day before the byelection - and did not feature a party logo or any form of promoter statement saying who had placed it.

It urged voters to vote for Mr Harawira rather than his main rival, Labour list MP Kelvin Davis, to get "two for one".

Mr Harawira confirmed it was his advertisement and said the lack of the promoter statement was a simple mistake.

The original copy of the advertisement sent to the paper had included the promoter statement, which was on Mr Harawira's other material.

However, the person placing the advertisement later sent the newspaper a change in wording without the promoter statement.

Under electoral law, every advertisement must carry a promoter statement, including who authorised the advertisement and their address. The penalty for wilfully failing to include a promoter statement is a fine of up to $40,000. Newspapers which publish election advertisements without promoter statements can also be held liable.

A legal adviser at the Electoral Commission said yesterday that it was not aware of the advertisement but had to investigate any such matter that came to its attention.

The advertisement was in the form of a box repeated four times in a strip along the bottom of the sports page. It read "A vote 4 Kelvin = Kelvin, A vote 4 Hone = Hone + Kelvin. Two for one! Vote Hone."

The Electoral Commission recently referred a Labour Party postcard to the police because its promoter statement was not in the prescribed form, although it did have Labour leader Phil Goff's contact details.

Labour tightened the rules requiring promoter statements in order to clamp down on anonymous campaigns, such as that run by the Exclusive Brethren in 2005.