National leader Judith Collins promised voters her party will be a "strong Opposition," following its first meeting as a caucus since its devastating election loss.
Her deputy leader, Gerry Brownlee, has also confirmed he would be staying on as an MP – on Sunday he raised the prospect of leaving Parliament after he lost is previously safe Ilam seat.
But his position as deputy leader of the party has not yet come up for discussion, he told reporters.
Nick Smith, who lost his long-held Nelson seat, also confirmed he would be staying on as an MP.
Today's caucus meeting was described as a "sombre" occasion by outgoing MPs.
It was the first time the caucus had met since Labour's landslide victory on Saturday.
National, however, achieved its second-worst election result in history, winning just 27 per cent of the total vote.
Speaking to reporters on their way into Parliament this morning, National MPs were clearly licking their wounds after the loss.
Outgoing MP Maggie Barry said the result was "horrible" – others described it as "disappointing" and some refused to talk to media altogether.
But much of the focus was on a major leak of internal party information just weeks before the election day.
An email from MP Denise Lee to the rest of caucus objecting to
Collins' decision to announce a review of the Auckland Council was leaked to a media outlet.
Collins said, according to its polls, that leak cost the party roughly 5 per cent of it support – or close to 120,000 votes.
Tim Macindoe, who lost the Hamilton West electorate and did not get back into Parliament on the list, said the person who leaked the information was responsible for the demise of some of their colleagues.
His message to the leaker was: "Shape up or ship out. Do not stick around, thinking you are in any way advancing the interests of the party by behaving in that despicable way.
Surviving MP Michael Woodhouse had a similar message, telling reporters that whoever was leaking "certainly needs to get loyal."
And Northland MP Matt King urged the leaker to "front up."
"Tell us who you are, so we can kick you out."
Collins entered the party's caucus room this afternoon flanked by all her remaining MPs.
She told reporters the leak would be part of an internal review of the National Party.
But she said National was now looking forward.
"It's onwards and upwards for us," she said. "I'm feeling positive about the way forward."
Asked specifically about the leaking from the caucus, Collins said it was "really clear that everyone has to work really well together".
"I'm very positive that we are going to have a very, very good caucus and we are going to be a very strong Opposition."
She said she did not think there were going to be "any issues" with leaking in the future as the caucus was "very focused".
Pressed again, she said: "I hope everyone does the right thing".
Collins said she has the full support of the caucus.