An advertisement endorsing outgoing Air New Zealand boss Christopher Luxon as a potential National Party leader should have had authorisation from the National Party, according to the Electoral Commission.

But the body says it will not be taking the matter further.

Last month, the Weekend Herald featured a half-page ad which compared Luxon to former Prime Minister John Key.

Underneath the caricatures of the two men were two hashtags: "#Luxon2020' and '#National2020'.

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It was later revealed property developer Steve Brooks had paid for the ad but did not have National's authorisation.

In a statement, the Electoral Commission said in its view the ad was a "party advertisement," as defined in the Electoral Act.

"[It] should have had the written authorisation of the National Party secretary prior to publication."

The Commission said it would not be taking the matter further.

NZME, the publisher of the Herald, accepted it should not have run the ad with the hashtag 'National2020'.

The Commission said steps were taken by NZME to establish Brooks did not have the required authorisation and the hashtag was removed from the online version of the advertisement.

But a staff error meant that the print version was not changed; NZME has given an undertaking that it would be reviewing its processes, the Commission said.

"A letter has been sent to Mr Brooks reminding him to seek advice on the content of any future political advertising.

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The ad came after Luxon announced he was stepping down as Air NZ chief executive.

In an interview with Newstalk ZB, he said he was weighing up a political career. "Politics is something I am interested in."

Asked whether his political party of choice would be National, Luxon said: "Yes I think it probably would be".

A 1News/Colmar Brunton poll on Monday showed that Luxon's was registering on the preferred Prime Minister rankings – although, he was only at 1 per cent.