The Government is getting "way ahead of itself" by talking about tax cuts after a single, small surplus, the Labour Party says.
Finance spokesman Grant Robertson predicted the Government's surplus, the first since 2008, would be a "one-hit wonder" because of changing economic conditions.
"The surplus show is over before it has begun," he said. "With the economy running out of steam, National's promises of a string of surpluses are extremely unlikely to become reality."
Prime Minister John Key said it was difficult to tell whether the surplus would be repeated. He noted that the Treasury's prediction in May of a $684 million deficit had turned into a $414 million surplus for the 2014/15 year.
Mr Key said there was no point in maintaining surpluses for the sake of it, but it was his preference to stay in the black to protect against another natural disaster or downturn.
Finance Minister Bill English could not say whether he would deliver further surpluses in coming years. He was wary of falling dairy prices, low inflation and an uncertain international environment.
Nevertheless, tax cuts proposed for 2017 were still on the table and could even be brought forward.
"I suppose that's possible," Mr English said.
"We put the allowance in there three years ago now, so we've always got the capacity to move that around."
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Mr Robertson said talk of tax cuts was premature.
"What we need to see is investment in growing jobs and growing a sustainable economy and keeping our regions going. Looking at tax cuts is getting way ahead of themselves."
He said under Mr English's economic plan, New Zealand would not begin paying down $60.6 billion net debt until 2019 or resume contributions to the Super Fund until 2021.
New Zealand's net debt amounted to 25.2 per cent of GDP, which Mr English said was low in OECD terms.
The surplus fulfilled one of National's key 2011 election promises.
Mr English said reaching the target was a "significant milestone" because it had been the Government's top fiscal priority over the past four years.
It reversed an $18.4 billion deficit following the global financial crisis and Canterbury earthquakes.
Mr Key praised his Finance Minister for reaching the target without "slashing and burning". Social services such as Working for Families, interest-free student loans and pensions had been left intact, he said. Mr Robertson disagreed, saying it had been reached at the cost of health and education, and because of delays in spending on the Christchurch rebuild.
"What's important is what the economy delivers for people. If the economy is delivering unemployment of 6 per cent and over 300,000 children in poverty, it's not working properly."
• $414m surplus for the 2014/15 year - the first surplus since 2008
• Higher than expected tax revenue of $66.6b, up $5.1b on 2014
• Lower than expected Govt spending of $72.4b, down 0.3% as percentage of GDP
• Net debt $60.6b, down 0.4% as a percentage of GDP