Green Party MP Elizabeth Kerekere has resigned her Covid-19 and health portfolios and apologised for breaking self-isolation rules.
Green MP Teanau Tuiono has been appointed Covid-19 spokesperson while Jan Logie has taken over health.
In a statement, Kerekere admitted flying from her Tairāwhiti home to Wellington on Sunday - despite a household member testing positive two days earlier.
She had tested negative for three consecutive days, but said she should have known better.
"I apologise profusely to my constituents, whānau, and colleagues for my mistake, and to everyone who is making huge sacrifices to follow rules that are designed to keep us all safe," the statement said.
Kerekere said she had apologised to her caucus and co-leaders - and wanted to extend that to her constituents and whānau.
Co-leader Marama Davidson said the party was disappointed with Kerekere's actions, saying she showed poor judgement.
"She has been testing every day, RATs, negatively and felt that was justification enough to come to Parliament... we're very clear that was wrong, that was a mistake, she should have known better.
"I am disappointed, of course. Any MP should know better but of course a Covid-19 spokesperson should absolutely know the rules. We've expressed that disappointment, we've accepted Dr Kerekere's apology for that mistake, we want to ensure that people can see that we are accountable to the public and we want MPs to be treated as anyone else breaching one of the health orders."
Davidson said Kerekere had offered to hand over the Covid-19 portfolio yesterday, and it became clear in Caucus discussions that "the right thing to do was to also stand her down from the health portfolio as well".
The Green Party has notified public health authorities of the rule breach and Davidson said further action would be taken based on the response.
Kerekere also apologised to health and essential frontline workers, and acknowledged Māori, Pacific and community providers and people who had underlying conditions or were immunocompromised.
"I know you are also feeling the compounding effects of this pandemic and are making difficult individual choices every day to stay safe," she said.
"The Green Party will continue to push for an equitable response to the Covid-19 pandemic and for Māori and Pasifika health providers to have the resources they need to keep their communities safe. I do not want my mistake to distract from this important kaupapa."
Davidson said Dr Kerekere had been an outstanding leader in the party's work, including in highlighting Māori and Pacific health inequities.
She said it was especially important for the leadership of wāhine Māori to be upheld
"That's also why I'm disappointed in how this action can undermine her incredible work in that space ... we look forward to being able to support her further work in any way that is appropriate to continue."
"We continue to uphold Dr Kerekere's incredible leadership across all of her work [but] this mistake she needs to be accountable for."