Updated 10.05pm:Â Winston Peters says his win sends a clear message to the National government that Northland voters feel taken for granted.
"This victory tonight will resound around the provinces, some of the suburbs of our big cities, because people know there is hope in politics when you put it all on the line."
The New Zealand First leader has won the previously-safe National seat by just over 4,000 votes.
"It just shows you that you should never ever think that something is not possible, if you've done the preparation and got the commitment."
Mr Peters says Mr Osborne called him earlier this evening to congratulate him,
"And I shared with him the fact that he was in the most impossible position, trying to make up decades of neglect. And it wasn't his fault, and I wanted his wife and family to know that."
AUDIO:Â Newstalk ZB Political Editor Barry Soper on Winston's huge win
It's a dire outcome for National.
Their Ministers, MPs and party faithful have been supporting candidate Mark Osborne in Kerikeri.
He says it's been a tough, brutal battle.
"I'm proud to have been part of this campaign, it's been a challenging campaign, and it's brought the best out of me I think. I don't think there's anything more that I or the team could have done."
AUDIO: Mark Osborne concedes defeat.

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National's Mark Osborne concedes defeat, flanked by his wife and National MPs. (Briana Watson)Â
With 100% of the vote counted, Winston Peters has 15,359Â votes compared to 11,347Â for Mark Osborne.
Labour's Willow-Jean Prime is in third, with 1,315 votes.Â
The Aotearoa Legalise Cannabis candidate nabbed more votes than either the Act or Mana candidates.
Northland has typically been a safe seat for the National Party, who have held the electorate since the creation of the electorate in 1996.
At the last election, National's Mike Sabin took home a majority of more than 9000 votes. He was forced to step down due to personal reasons earlier this year.Â
However, polling in the week leading up to the election gave Winston Peters a lead of 20 percentage points over Mark Osborne.
Guests at the New Zealand First HQ, the Duke of Marlborough Hotel in Russell, include former Labour MP Shane Jones, along with various current NZ First MPs.

Shane Jones at the New Zealand First gathering in Russell (Annabel Reid)Â
The National Party gathering in Kerikeri includes senior Ministers Steven Joyce and Paula Bennett, along with other National MPs.
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