Canterbury's earthquake rebuild programme is ramping up to noticeably strengthen the country's economic growth, economists say.

But growth in the quake-hit region is still patchy, with construction booming but other sectors like retail remaining weak.

In the year to June 30 New Zealand's economy measured by gross domestic product expanded by 2 per cent, meaning growth was at the fastest rate since the National-led Government came into power.

The 2 per cent growth was the best since the year to March 2008 when there was GDP growth of 2.5 per cent.

The boom in Canterbury's construction sector responding to earthquake repairs and heavy and civil engineering work, such as the construction of roads, bridges and sewerage, were cited as having influenced the national GDP pickup.

Canterbury's regional economy contracted after February 22 and June 13 earthquakes in 2011.

The Canterbury Earthquake Recovery Authority (Cera) believed regional GDP for Canterbury had recovered to pre-earthquake levels.

Figures from the National Bank show regional GDP for Canterbury growing by 4.4 per cent in the year to June 2012, a Cera spokesman said. This represented the strongest rate of annual increase for any individual region since 2007.

Economists had expected national growth of around 0.3 per cent in the three months to June 30, but the Statistics NZ figures showed a higher 0.6 per cent growth in the quarter.

Agriculture, up 4.7 per cent, was the largest contributor to New Zealand's economic growth in the June quarter, with construction up 3.3 per cent and manufacturing up 0.8 per cent.

Yesterday, UBS New Zealand senior economist Robin Clements said there was a notable buildup in quake-related residential and commercial construction work, and other influences on the GDP including Canterbury civil engineering work.

That boost was a feature that should be repeated, not necessarily quarter after quarter but over time.

While it was still possible to get a builder to do repairs at this point, after Christmas it would be much harder to do so, he said. Multiple housing subdivisions in Christchurch were selling fairly quickly, with signs that insurance issues were being resolved.

"We know there's a lot more to be done. We know that the ramp-up is only in the early stages so it's increasingly going to be a feature of the growth data over the next year or two."

At some point the rebuild would result in double digit growth, and there were already some measures pointing towards quarter on previous corresponding quarter growth of 6-7 per cent, Clements said. "I would imagine within a year we will be able to say some measures are pointing to double digit growth in Canterbury."

ASB bank economist Christina Leung said a large part of the stronger-than-expected 0.6 per cent quarterly growth reflected the boost from post-earthquake rebuilding, with large increases in construction and core manufacturing output.

Shamubeel Eaqub, NZIER's principal economist, said his estimates suggested that the growth in Canterbury in the year to June 30 had not been exceptionally strong.

- © Fairfax NZ News