Several complaints have been made about the tweet, the Electoral Commission has confirmed to media.

It's against the Electoral Act to publish or distribute statements that may influence voters on election day, until booths close at 7pm - including on social media.

Last election, several tweets from public sportspeople that endorsed National were referred to police. Warnings were issued, but no prosecutions were made.

Mr Plunket was the communications director for TOP at the time of the tweets. The party ended up with 2.2 percent of the vote.

He claims to have left the site at midnight on Monday, promising to "visit and observe" but not to tweet anymore.

"Bye," was what appears to have been his final tweet.