Growth in the services sector reached a nine-year high in July, marking three years of unbroken expansion, as new business rose to levels last seen a decade and a half ago, a survey has shown.

Investec Purchasing Managers' Index of activity in services, which covers businesses from banks to hotels, rose to 63.4 in July from 63.3 in June. 

The new business sub-index climbed to 66.2 from 63.7 in June, the third-highest mark since the series began in 2000.

The index has stayed above the 50-point line that separates growth from contraction since July 2012. A comparable survey gave a reading of 54.0 for the euro zone a whole.

"It is clear that services firms in Ireland retain a high degree of optimism on the outlook for their sector," Investec Ireland chief economist Philip O'Sullivan said.

"Given the improving dynamics around the domestic economy and the continued tailwind to exports from favourable FX moves, we believe that this positivity is well-founded."