The Tasmanian Government is again under fire over its water and sewerage changes with Opposition claims some development costs have doubled.

Opposition spokesman Peter Gutwein has attacked the Government for months over bill increases from the new water corporations.

Today he raised the issue of headworks charges to install water services on new blocks.

Mr Gutwein told parliament the charge had doubled in one case to $10,000 and ordinary Tasmanians were again bearing the brunt.

The Treasurer, Michael Aird, says headworks charges were included in the legislation, supported by the Liberals.

The Acting Premier, Lara Giddings, told parliament health considerations alone made change essential.

"On average every day there is sewerage that is spilling somewhere in Tasmania," she said.

"That is unacceptable in the modern era."