"It's just not good enough.
A spokesman for the Prime Minister's office said Labour's accusations were "nonsense".
"The Prime Minister has to balance his time with New Zealanders in the community against the huge media demands during the campaign."
But Mr Robertson said New Zealanders "rightly want to quiz him on why he has not delivered on his promises", such as closing the wage gap with Australia, stopping the exodus of New Zealanders across the ditch and helping New Zealand's "underclass".
"But they are not being given the chance as he continues to refuse to debate substantive issues and his record in government.
"Elections are meant to be a contest of ideas where the public can scrutinise each party's record and hear their plans for the future.
"Labour is up for it. Why isn't John Key?
"If he's proud of what he has done and what he wants to do then he should stop hiding and face up to the hard questions."
- HERALD ONLINE