Bill English: Why I'm standing for Prime Minister

Deputy Prime Minister Bill English confirmed he will run as National Party leader to replace John Key.

English agreed that it was time for regeneration in the National Party "and that's what we are doing."

"Regeneration is about the ability to deliver in the circumstances of 2017 through to 2025 and we're very well set up for that," he told reporters at Parliament.

He had not made any decision about running on a ticket with a possible deputy - Paula Bennett has been tipped to be his deputy but she is thought to be considering a run herself.

He said he wasn't taking a win for granted. He had had plenty of indications of support but that was a matter that would be refined over the next few days.

"Most important in our team is the energy to go forward," said English.

"I've been in a previous third-term Government and this, as fostered by John Key, is a team with a lot of energy in its leadership."

Discussion is all about looking at the next five to 10 years."

English ruled out being Finance Minister and Prime Minister at the same time.

Asked if he could remain Finance Minister for someone else if he lost the leadership contest, he said he had not thought about that.

He said New Zealand was growing strongly.

"We want to see many New Zealanders receive the benefits of that growth in their incomes and their opportunities and we want to get a better path for the most disadvantaged and vulnerable."

He said he would not be making any declarations as John Key did about not touching superannuation.

That was a matter for the duly elected leader of the National Party.

English said he did not see the actions and style of the Government changing very much, "one that takes the public along with us, maintains public support which earns the right for more and better change, so we can improve the economy and change people's lives."

Speaking about his unsuccessful stint as leader in 2002 when National polled only 21 per cent he said the circumstances were different.

He said that at the time he was a father of six children under aged 13. His youngest now was aged 17.

He acknowledged that leadership contests could be divisive but said there was as strong commitment from the caucus for a process the get the leader they wanted "while at the same time as maintaining the kind of cohesion and stability they have got used to."

"They understand how effective it is. One of the reasons we have been a well supported Government is because it has been such a disciplined caucus.

"They know that any signs of that loss of discipline are not going to help their political support.

"Unity is everything is this business."

English said that Coleman managed the biggest and hardest public agency in Government, Health, "and he does that very competently."

"I've always known he was ambitious so he is welcome to have a go."