Todd Muller has announced his immediate resignation as leader of the centre-right National Party, saying "I am not the best person" for the position.
New Zealand's opposition leader abruptly has quit citing health reasons just weeks after taking the job, leaving his party in disarray with an election against incumbent Prime Minister Jacinda Ardern looming.
In a brief early-morning statement, Todd Muller announced his immediate resignation as leader of the centre-right National Party, saying "I am not the best person" for the position.
The 51-year-old ousted his predecessor Simon Bridges in late May but failed to reverse polls showing strong backing for Ardern ahead of the September 19 election.
"The role has taken a heavy toll on me personally, and on my family, and this has become untenable from a health perspective," he said.
Muller did not detail his health issues but New Zealand Herald political editor Audrey Young said that he had struggled to cope with the high-profile role.
"The words 'mental health' have not been used but Muller has had a breakdown, to the extent that he was unable to even make the emergency teleconference caucus call this morning to tender his resignation," she wrote.
Radio New Zealand reported that Muller had isolated himself from staffers and colleagues in recent days as pressure mounted.
Ardern passed on her best wishes to Muller and his family.
"No matter what side of parliament you're sitting, politics is a difficult place," she said.
Muller's National Party colleagues, who will meet later Tuesday to discuss a replacement leader, offered comfort.
"Our thoughts are very much with Todd and his family at this difficult time as is our compassion and love for Todd," the party's senior whip Barbara Kuriger said.
First story for today about a bombshell in NZ🇳🇿 politics: One of the shortest leaderships in the country's modern history as Todd Muller stands down from head of the National Party after 53 days: https://t.co/fsTFjKW1LP— Justin Giovannetti (@justinCgio) July 13, 2020
The National Party has been embroiled for the past week in a scandal after it was revealed a junior lawmaker leaked private health details of New Zealand Covid-19 patients to news media.
The information was provided by a former party president who received it confidentially in her capacity as acting chief executive of the Auckland rescue helicopter organisation.
Muller has been widely criticised for his handling of the scandal and the veracity of some of his statements had been challenged.
He was facing questions over when he knew the source of the leak and if he knew one of his most senior MPs had also received the information.
The private information was sent to three media organisations but was not published.
Muller faced a thankless task confronting Ardern, who has won widespread praise for a Covid-19 response that has limited New Zealand to just 22 deaths in a population of five million.
He clawed back some support for the National party, taking it to 38 percent against 50 for Ardern's Labour in opinion polls, but still trailed 13 percent to 54 in the preferred prime minister rating.
Muller was highly critical of Ardern when personal details of active Covid-19 cases were sent to the media, but the attack backfired when it emerged last week that the leak came from a member of his own party.
Muller said he would now "take some time out of the spotlight" with family but intended to remain in parliament.
Former Air New Zealand chief executive Christopher Luxon, who is standing for a parliamentary seat in the September election, is also a potential replacement in the longer term.