Bill English has been re-elected unopposed as National Party leader and says he intends to lead the party into the 2020 election, claiming National is "the strongest opposition the New Zealand parliament has seen".
Mr English, flanked by re-elected deputy Paula Bennett and senior whip Jami Lee Ross, told reporters National "will go into opposition with more seats than the Labour-New Zealand First coalition government with 56 seats on our side".
Mr English told reporters he has committed to leading an opposition "that will make sure the benefits New Zealanders have worked so hard for in our economy are not just preserved but continue to improve".
He said people have done a lot of work over the last 10 years to get to being one of the better performing economies in the developed world.
"The policies we are seeing from the incoming government could fritter that away. We will hold them to account on the high expectations they have created that for instance incomes will rise faster and that they will make better progress on some of the more challenging social and environmental issues," Mr English said.
"We don't believe their policies point in that direction."
Mr English said the National opposition have a more positive view about New Zealand's prospects than the incoming government which has already set out to prepare people for a slowing economy and at the same time promising higher incomes.
"I think they'll find that a bit of a challenge."
He said the release of the coalition agreement today needs to be seen in the context of the agreement with the Greens and with Labour's policies which are the most significant of the government.
"Taken as a whole, in the first place they look really quite expensive, so we'll be tracking closely the impact on on the government books and the impact of the significantly increased expenditure and whether it achieves results," he said.
"The policies also look to shift the economic direction somewhat and we’ll be holding the government to account on whether the broad sweep of the policies that is Labour, Greens and NZ First achieve the kind of greater economic performance that they’ve claimed."
Bill English was prime minister for about nine months, winning National's leadership election unopposed following the resignation of John Key last December.
Despite winning the largest share of the party vote, 44.4 per cent, in last month's election, National is now in opposition after New Zealand First last week opted to go into coalition with Labour, which will be supported by the Greens on confidence and supply.