Manitoba Hydro's decision to build a power-transmission line down the west side of the province's great lakes will now cost more that $1 billion than originally estimated, Opposition politicians charged on Monday.

In 2007, the NDP government announced the $2 billion project would be built on the west side of Lake Winnipeg to preserve a boreal forest on the east side. In doing so, it over-ruled Hydro's original plans.

'It's a staggering level of waste.' —Hugh McFadyen, leader of Manitoba's Progressive Conservatives

But that decision meant the power line — dubbed Bipole III — would cost an extra $640 million because it would have to be longer than if it was constructed on the east side of the lake. The western route is 50 per cent longer.

On Monday, Progressive Conservative leader Hugh McFadyen said Hydro has confirmed to him the west side construction will also add $1.1 billion to the project's cost because custom power-conversion equipment will be needed.

During question period at the Legislature, McFadyen called on the government to reverse its decision about building Bipole III on the east side.

"It's a staggering level of waste and a completely irresposible decision, which is the bad news," McFadyen said. "The good news is there is still time to reverse it," he said.

But Premier Greg Selinger countered by saying that the conversion equipment was always expected to be needed.

"Manitoba Hydro made it very clear three years ago that converters are a likely requirement no matter where … Bipole went. There is nothing new here," Selinger said.

Revenues to justify cost: Selinger

The transmission line will begin at Gillam, in northern Manitoba, run west of Winnipegosis and Lake Manitoba and end at a new converter station east of Winnipeg.

Manitoba Hydro had originally planned to run the line east of Lake Winnipeg, but the plan was overruled by the provincial government in 2005 due to environmental concerns raised by aboriginal people living in the area.

More than 75 per cent on Manitoba Hydro's electricity production is currently supplied through two existing lines that run from Gillam through the Interlake to Winnipeg, Hydro officials said.

The new line would act as a back-up to the current system and be able to carry power from new generating stations, including Conawapa, to southern Manitoba and the province's export markets.

Selinger said Bipole III could produce up to $20 billion in revenue for the province in its first 20 years of operation.

The expected completion date is 2017.