Bay of Plenty MP Todd Muller has won the support of the National Party caucus, defeating Simon Bridges in a vote for party leader this afternoon.

National MPs have been in a closed meeting this afternoon to decide who the next leader will be to take National to the September Election.

The leadership challenge came after two polls one putting National at 30 per cent and the other at 29 per cent - numbers not seen since the early 2000s under Bill English. Labour's party vote skyrocketed to a record 59 per cent.

Simon also took a dive in the preferred Prime Minister stakes, dropping six points to five per cent, against Jacinda Ardern on 63 per cent.

Auckland Central MP Nikki Kaye has been elected as the new deputy leader.

'There is no Team Todd, there is no Team Nikki, or anyone else – there is only Team National,” says Todd.

'National has always been a coalition of city and country, business and community, conservatives and liberals – National is the party for all New Zealanders.

'New Zealanders need a National Government with the experience and management skills to get our country through the worst crisis since the end of the Second World War.

'My focus as leader is our country's economic recovery and the strengthening of every community throughout New Zealand.”

The country is four months away from the 2020 general election.

This week moved fast for National MPs who saw their party's ratings dip in two polls, and followed by a summon to the Capital to vote in their preferred leader - Bridges or Muller.