Sri Lanka's apex court today ruled as unconstitutional an attempt by ruling UPFA coalition's legislators to impeach the nation's first woman chief justice, escalating the tussle between the legislature and judiciary.

A three-judge bench of the Supreme Court ruled that a Parliamentary Select Committee (PSC), which probed the impeachment charges against Chief Justice Shirani Bandaranayake, has "no legal power or authority".

"The Supreme Court determined that the PSC had no legal power or authority to make a finding of guilt or decision affecting rights of a judge since that is a power that has to be conferred by law and not standing orders of parliament", a lawyer told reporters.

The judgement was delivered in response to a plea filed by Bandaranayake in the country's Appeal Court seeking to quash the PSC findings, which ruled her guilty.

The parliamentary committee on December 8 ruled that Bandaranayake was guilty of three of the 14 charges in the impeachment proceedings against her moved by the ruling UPFA coalition legislators.

The three charges were financial impropriety based on non declaration of assets and conflict of interest in a case involving a failed investment company.

The 54-year-old chief justice denied all the charges against her. On December 6, she stormed out of the impeachment hearing in parliament, saying she will not be given a fair trial. The opposition had also boycotted the PSC, claiming the whole process a political witch hunt.

The impeachment which brewed over several months was the result of a tussle between the judiciary and the government.

The government claimed the Supreme Court was acting against it while the judiciary claimed its independence was being attacked by government.

President Mahinda Rajapaksa appointed Bandaranayake as the chief justice in 2011. The move to impeach Bandaranayake came after she scuttled several bills, including one that gave more powers to the President's brother Basil Rajapaksa, the economic development minister.

The court ruling, however, is certain to be ignored by the Parliament, analysts noted as it had at all times held that its powers were supreme and no court has jurisdiction over parliamentary action.