He called the policies agreed by the three parties "very confused and contradictory and grab bag of commitments that will ultimately take New Zealanders backwards".
The National, New Zealand First and Act New Zealand coalition was unveiled this morning.
Hipkins said the new government prioritised landlords over renters, the oil and gas industry over New Zealand's international reputation, and the tobacco lobby.
"We've also seen that even before they go into government, our predictions before the election that their tax cuts didn't add up have, of course, proven true," Hipkins said.
"They've been completely silent about how they're going to pay for that."
Hipkins said additional borrowing was likely so the new government could fund its tax cuts.
"That means inflation will stay higher for longer, interest rates will stay higher for longer, and ultimately, New Zealanders will pay more than they're likely to benefit from the tax cuts the National Party is offering.
Hipkins said Act leader David Seymour and NZ First's Winston Peters had been "running circles" around National leader Christopher Luxon over the past few weeks.
He said we had seen the "seeds of some very divisive debates" from the new government.
"This is definitely going to be a government that drives New Zealanders apart and leads to more polarisation of the country than we have seen to date," he said.
"They already committed to very, very significant reductions in government department expenditure, and now they're saying they think they can find more. At the same time, they're also making commitments to spend more money as well.
"There is no plan. There's a reason for that, over the past six weeks they've come up with a whole lot of commitments but have no idea how they're going to pay for them."
He said Labour's role as in opposition would be to hold the government to account, to propose "better ideas" and to put itself in a position to win the next election.
"I'm very disappointed that, across the totality of agreements announced today, we've seen a real attack on workers. We've seen millionaires prioritised over workers," Hipkins said.
"Their plans to repeal a whole variety of provisions in our employment laws will ultimately help to drive wages down in New Zealand, leaving workers worse off," he said.
"That's the nature of democracy," Hipkins said of coalition talks and the election result. "I don't think New Zealanders necessarily voted for all the commitments in all of the agreements we've seen today, though."
He said parties would be switching offices around the Parliamentary precinct over the weekend.
He said his caretaker government would work with the incoming government to ensure a smooth transition.
The Labour Party leader has remained in the job since October's election as caretaker, awaiting the outcome of negotiations between the three parties, which will soon take over with Christoper Luxon as prime minister and Winston Peters his deputy.
The negotiations were the second-longest in New Zealand's MMP history, behind only 1996, when New Zealand First was in a 'kingmaker' position.