Jacinda Ardern was officially sworn in on Thursday as the 40th Prime Minister of New Zealand promising to tackle climate change, eradicate child poverty and improve the lives of the countrys most vulnerable people.Ardern, 37, received a round of applause from her cabinet, friends and family who had gathered at government house for the event, reports the Guardian.In her first comments as Prime Minister, Ardern promised to form an "active" government that would be "focused, empathetic and strong".A number of Ardern's cabinet chose to take their oath to the crown in Te Reo (Maori language), including deputy Labour leader Kelvin Davis, Minister for Maori development Nanaia Mahuta and Women's Minister and Greens MP Julie Anne Genter, who is originally from the US.After the swearing in ceremony, a crowd of around 1,000 people gathered on the lawn of Parliament house to greet Ardern, the third woman to lead the country and the youngest Prime Minister in 150 years.Ardern was elected leader of the Labour party less than three months ago after previous leader Andrew Little tanked in the polls. She was picked as the only hope for the beleaguered party to enter government, the Guardian reported.Ardern told the crowd: "We vow that regardless of who you voted for, regardless of where in Aoteroa you live, this will be a government for all New Zealanders."