The spat between Cook Islands and New Zealand bubbled over in parliament on Wednesday (AEDT), when Mr Brown beat a no-confidence vote 13-9.
In a sensational defence, Mr Brown accused Wellington of trying to "control" his country, and treating it like "a child".
The leader has ruffled feathers with two proposals in recent months: an abandoned bid to create Cook Islands citizenship and issue their own passports, and a economic pact with China which NZ alleges was negotiated in secret.
The Polynesian nation has a special relationship with New Zealand that sees Cook Islanders receive the benefits of Kiwi citizenship in exchange for consultation on key matters.
Opposition parties brought the no-confidence motion arguing Mr Brown had jeopardised relations with New Zealand, its former colonial partner and most influential development partner.
"We want to stand on our own two feet and make our own decisions, but there's a big 'but' there," Teariki Heather said, as reported by Reuters.
"Who has supported us during the past? Our relationship with New Zealand."
The ties between the two countries remain profound, with 20,000 Cook Islanders living in the Polynesian nation but a further 100,000 in New Zealand, owing to the freedom of movement.
Mr Brown told parliament it was his responsibility to seek out "every opportunity that benefits our people".
"Just as New Zealand and Australia and other nations pursue economic partnerships that serve their national interest, we too must act in our own personal interests," he said.
He accused the New Zealand government of dishonest messaging, and said the subtext was "not about consultation, this is about control".
"We cannot compete with New Zealand. When their one-sided messaging is so compelling that even our opposition members will be swayed," he said.
"We never once talked to the New Zealand government about cutting our ties with New Zealand but the message our people received was that we were cutting our ties with New Zealand.
"We are a partner in the relationship with New Zealand. We are not a child."
Mr Brown fell out with New Zealand Foreign Minister Winston Peters over the covertly negotiated pact, and earlier this week attacked the Kiwi media for its reporting of the affair.
"The implication being that we are too dumb to know what we're doing," he told the Cook Islands News.
Mr Peters has since declared that relations between the two countries require a "reset", and on Wednesday, said it was the right of Cook Islanders and MPs to decide their relationship with New Zealand.
The Cook Islands-China pact includes a five-year action plan and three memorandums of understanding to deepen economic ties and build infrastructure, though Mr Brown said there had been "no commitments made as yet" on specific projects.
One contentious part of the deal is an agreement to co-operate on deep sea mining, which does not enjoy support among many in the Pacific due to its unknown environmental impacts.