"The proposed route passes immediately next to the lake, through an area of frequent seismic activity. That cannot be anything but worrying," Itar-Tass news agency quoted speaker Viktor Kruglov as saying.

He said the oil company constructing the pipeline, Transneft, had not consulted the regional parliament about its plans.

Some sections of the 4,000-kilometre (2,500-mile) pipeline will pass as close as 800 metres (yards) to the lakeside, ecologists say.

Carrying oil east from Siberian fields to the Sea of Japan, the pipeline project is Russia's biggest yet, involving investments of between 11 and 17 billion dollars (nine and 14 billion euros.)

Situated in southeastern Siberia, Lake Baikal is the oldest and deepest lake in the world, with 20 percent of the world's total unfrozen fresh water reserve. Its age and isolation have produced one of the world's richest and most unusual fresh water flora and fauna.

Kruglov's criticism added to protests about the pipeline from the governor of Siberia's Irkutsk region, ecologists and Russian official experts.

The experts said in January that Lake Baikal, which is classed by the United Nations as a World Heritage Site, was seriously under threat from the planned Siberia-Pacific pipeline near to its shores.

They said as much as 4,000 tonnes of oil could be discharged into the lake if there were an earthquake, a scenario confirmed by Trasneft vice-president Sergei Grigoryev.

Transneft officials subsequently said the company would use piping three times thicker than the standard nine millimetres (0.35 inches).

In addition to earth tremors, ecologists say human error, attempts to steal oil or extremist attacks could also lead to devastating oil spills that would affect both the environment and human health.

But Russia's Supreme Court ruled in favour of the pipeline route on March 9, just days after a commission created by Russia's environmental office reversed its earlier decision to reject the plan.

A member of the commission told AFP its members were facing pressure to approve the route of the pipeline, which is seen by supporters as a crucial way of increasing exports of Siberian oil to the booming Asia-Pacific market.

Construction is expected to begin in July.

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