Close to $1 billion budgeted to roll out the state government's flagship Service NSW customer centres will not be recouped from savings under the program for over 10 years – at least three years later than planned – a review has found.

The KPMG review also reveals spending on a key aspect of the rollout of the centres – which offer services from drivers license renewal to marriage certificates – ran well ahead of budget in 2015-16, prompting Opposition claims of a $96 million blowout.

Premier Gladys Berejiklian says Service NSW centres are providing better customer service. Credit:Brook Mitchell

Operational expenditure on the Accelerated Distribution Strategy (ADS) was $51.9 million higher in 2015-16 than anticipated, according to the report handed to Service NSW in February.

Capital expenditure was $53.8 million higher than anticipated for that year in the ADS business case written in 2014. There was a combined $9.4 million underspend in 2014-15.