Peter Dunne should have used his political muscle to stop TVNZ7 being shut down, Labour says.
The United Future Party leader has criticised the closure and says the government's decision to stop funding it was "inconsistent and wrong".
Labour's broadcasting spokeswoman Clair Curran says his comments were "simply posturing" and he should have used his political leverage to save the channel.
"You'd think the great champion of public broadcasting would have made a bit more of an effort when he negotiated a support agreement with the government late last year," she said on Monday.
"Broadcasting Minister Craig Foss' actions are inconsistent and show a serious lack of strategic planning - but at least he's upfront with his indifference."
Mr Dunne's support agreement commits him to supporting the government on confidence votes, like the budget, but he can disagree with it on anything else.
TVNZ7 was the country's only commercial-free channel and it closed on Sunday night.
A lobby group is trying to save it but admits there's not much it can do because it hasn't got the money for legal action.
It is going to lay a complaint with the ombudsman arguing that TVNZ acted unlawfully when it axed the channel.