The Berejiklian government extracted almost 40 per cent profit from key state-owned companies in the past financial year even as two of the main utilities reported a large share of unplanned repair works.

The details of the jump in Treasury's take, particularly from Sydney Water and Hunter Water, were revealed in the Auditor-General's report for 2017-18 released this week.

'Unplanned maintenance works - such as this burst water main in Botany earlier this month - are on the increase in NSW, the Auditor-General says in a report. Credit:Peter Braig

State-owned corporations provided $1.3 billion to the government, up from $954 million a year earlier. Just three agencies, Sydney Water, Hunter Water and Landcom lifted "distributions" by $392 million.

Sydney Water, which supplies water to the metro region, raised its pre-tax profit by 28 per cent to $814 million, thanks to higher water charges and lower borrowing costs, the report said. Hunter Water increased its profit by about half the rate, or 14 per cent, to $94.3 million.