Water users paying too much, Paul Kerin tells SA parliamentary committee

South Australian households are paying up to $150 million too much collectively for their water annually, a former head of the Essential Services Commission claims.

Appearing before a parliamentary inquiry in Adelaide, Paul Kerin said the high charges effectively propped up the Government's budget.

Dr Kerin said Treasury officers bullied and intimidated his office and ignored advice which could have lowered prices.

His resignation letter revealed he quit the Essential Services Commission of SA (ESCOSA) in April because of frustration with the Government.

Now he has detailed that dissatisfaction to the parliamentary committee.

"It's really that decisions weren't made in the public interest and they were made abusing due process and with inappropriate behaviours," he said.

He claimed the Treasury Department micro-managed ESCOSA, ignoring its role as the independent regulator.

Dr Kerin told the committee the officials displayed appalling behaviour, made recommendations to Government against the Commission's advice, and this ultimately increased water prices and protected the state budget's revenue.

He said Government efforts to let the Commission reform pricing were a sham.

Charges 'inflated' due to value of SA Water assets

One complaint was that Treasury forecast a higher annual demand for water than the Commission forecast.

Dr Kerin also said the Government refused to write down the value of SA Water's assets and that inflated charges.

"If it's overvalued by $2 billion, and that's probably conservative, water consumers out there are paying an extra $150 million a year, every year," he said.

Treasurer Tom Koutsantonis hit back at the criticism.

"It's an argument made by someone who doesn't set policy, it's made by someone who has a political agenda to run. He wants to see our assets privatised," he said.

Opposition frontbencher Rob Lucas said Dr Kerin seemed to be on the side of consumers.

"I think consumers rightly will be furious because, in the end, what Dr Kerin is saying is they're paying hundreds of millions of dollars more for water and sewerage prices than they should," he said.

Dr Kerin threatened to quit in 2012 over what he called misleading comments by then treasurer Jack Snelling.

"He said ESCOSA did want to jack up supply charges and we did want to hurt small consumers [but] those statements were false," he said.

Mr Snelling denied the allegation.

"I've never done that. I'm always honest with the South Australian public and I take umbrage at any suggestion otherwise," he said.

Dr Kerin urged the parliamentary committee to call former water commissioner Robyn McLeod, whom he said had similar dealings with Treasury.