Former Liberal upper house leader Phil Davis' comments come as opposition leader Ted Baillieu appears almost certain to propose a dam as part of his 2010 election campaign.

Mr Baillieu has repeatedly hinted that dams are on his agenda, saying there were numerous possible sites across the state and he would "look at them all".

"We will be prepared to commit to new dams," he said on November 24.

Gippsland is home to most of the rivers that will be closely considered by Mr Baillieu, including the Mitchell and McAlister rivers.

But growing support for a new dam within Coalition ranks has been stalled by Mr Davis, who said the health of the Gippsland Lakes would suffer if one of the region's tributary rivers were dammed.

"The view that more water from rivers can be captured regularly and diverted from rivers in the catchment is unacceptable because of the damaging impact that would have on the lakes and the wetlands and therefore threaten their long-term ecological health," he said.

Mr Davis said those calling for Gippsland rivers to be dammed ignored "any understanding of the interdependency of Australia's icon inland waterway with its catchment."

Mr Davis said his comments did not split the Coalition because there was no current plan to build a new dam on a Gippsland river, nor did he expect such a policy.

But his stance was rejected by Mr Baillieu, who said "all" options would be considered.

National Party leader Peter Ryan also refused to back Mr Davis' suggestion.

The split comes after the Opposition was forced to backflip over its North-South Pipe policy in September, with Mr Baillieu conceding that he would take water through the pipe in an emergency.