President Rolandas Paksas denies any wrongdoing

It found Mr Paksas had violated the constitution by granting citizenship to a Russian businessman, and by leaking classified information to him.

The president says he has done nothing wrong and has refused to resign.

The scandal has embarrassed Lithuania ahead of its entry to Nato this week, and to the European Union on 1 May.

Parliamentarians say a final impeachment vote may be taken before Lithuania joins the EU.

'Gross violation'

Delivering its ruling, the court said Mr Paksas had "grossly violated the constitution".

The controversy started last October, when the state security department accused the president and his advisers of having links to Russian organised crime.

A parliamentary commission claimed the president posed a threat to national security, leaked state secrets and let top aides abuse their office.

Twice a former prime minister, Mr Paksas has said the accusations are a plot by his political enemies.

In recent months, the 47-year-old president has been touring the country, rallying his supporters.