New Zealand's services sector maintained a healthy rate of growth last month, according to the latest performance of services index (PSI) out Monday.

The BNZ-Business New Zealand PSI for June was 58.2, up 0.1 point from May, on a scale where above 50 indicates expansion and below 50 contraction.

It was also the highest overall value since July last year.

Business New Zealand chief executive Phil O'Reilly said in a statement that the consistent level of expansion over the first six months of 2015 had been helped by both activity/sales and new orders remaining within a fairly tight band of expansion.

"Combined with the improved PMI (performance of manufacturing index) reading for June (55.2) the latest PSI paints a picture of an economy expanding robustly, probably a little better than average," BNZ senior economist Craig Ebert said in the statement.

The gross domestic product-weighted performance of composite index, which combines the PMI and PSI, was up 0.6 points in June to 57.8.