As the outperformance that earned New Zealand the status of 'rock star economy' begins to wan, the government should focus on ensuring a 'rock solid' economy, New Zealand Treasury Secretary and Chief Executive Gabriel Makhlouf told CNBC on the sidelines of the Group of 20 meeting in Australia.

New Zealand bucked the poor global growth trend over the past few years, posting a strong economic performance as a series of headwinds dragged growth elsewhere. It grew an annual 3.9 percent on year in the second quarter - the fastest rate since the second quarter of 2004. However, on a quarterly basis the economy expanded 0.7 percent, slowing from three consecutive quarters of growth of 1 percent or more and suggesting a peak in the current growth cycle.

Meanwhile, in August, Makhlouf said the New Zealand government will reach its budget surplus forecast this fiscal year but noted that future surpluses could be lower than expected as economic activity is weaker than forecast in May. The budget has been in deficit since 2009.

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"We're forecasting that [the strong growth performance] will taper off a bit but we certainly want to move from being described as a 'rock star economy'... to being a 'rock solid' economy," he told CNBC.

"The government that was in place until now, its plans are pretty clear and credible in terms of its fiscal strategy and the reforms it wants to make to the way public spending is done. So I'm pretty confident actually that... on the current trajectory we'll continue to see growth in New Zealand and a more robust economy," he said.

While growth may have peaked at home, Makhlouf said the global economy is the biggest risk for New Zealand.

"What happens in Europe, which we are concerned about, the extent to which U.S. growth is sustained, what happens in China, which is now our biggest trading partner, and Japan and the rest of the world - global risks are the main risks to a small economy like New Zealand, and we're keeping a very close eye on that," he said.

Kiwi dollar

The New Zealand dollar outperformed its peers in the first half of the year driven by strong domestic economic momentum, central bank interest rate hikes and the country's terms of trade, which is at a 40-year high. However, currency strength has been a cause for concern at the central bank.

After hiking rates at its June policy meeting, the Reserve Bank of New Zealand (RBNZ) said the New Zealand dollar's level was "unjustified" and "unsustainable", raising expectations that it could intervene to weaken the currency. In September, the kiwi dollar weakened to a seven-month low against the U.S. dollar after the RBNZ said it expects "a further depreciation, which should be reinforced as monetary policy in the U.S. begins to normalize."