* Former Hungarian supreme court chief brought case
* Accused government of weakening judicial independence
* His removal had "chilling effect" on free speech -ECHR
* Hungary says considering response to ruling
By Gilbert Reilhac
STRASBOURG, France, May 27 (Reuters) - The European Court of Human Rights ruled on Tuesday that Hungary had sacked one of its most senior judges for criticism of the government, a ruling likely to heighten EU accusations of a power grab by Prime Minister Viktor Orban.
The decision's impact will be mainly symbolic - the ECHR imposed no punishment on Hungary although it reserved the right to rule later on reparation payments to Andras Baka over his dismissal three years before the end of his mandate.
Orban's critics, including some senior figures in the European Union, allege that he is concentrating too much power in his own hands while sidelining any possible challengers.
Orban's government, re-elected by a landslide last month, rejects those allegations. A spokesman, Andras Giro-Szasz, said the government would assess the ruling from the European court and "make a decision, if necessary". He did not elaborate.
The case was brought to the Strasbourg-based court by Baka, who was president of the Hungarian Supreme Court from June 22, 2009 until Jan. 1, 2012.
His mandate was terminated early when sweeping new legislation came into force that lowered the retirement age for judges, gave the Supreme Court a new name and revamped the role of the court's president.
In the months beforehand, Baka had spoken out repeatedly in public, raising questions about the impact of the new legislation on the ability of the judiciary to function effectively and independently.
"The early termination of the applicant's mandate as President of the Supreme Court was a reaction against his criticisms and publicly expressed views on judicial reforms," the ECHR said in its ruling, which was released on Tuesday.
Ending Baka's mandate early, the court found, "thereby constituted an interference with the exercise of his right to freedom of expression."
It ruled that Baka's removal did broader damage to democratic freedoms in Hungary, a formerly communist central European state that joined the EU in 2004.
"The fear of sanction has a 'chilling effect' on the exercise of freedom of expression and in particular risks discouraging judges from making critical remarks about public institutions or policies, for fear of losing their judicial office," the ruling said.
Orban was re-elected in April to a second consecutive term as prime minister, with his centre-right Fidesz party winning two-thirds of the seats in parliament.
He has argued that he has a democratic mandate to reform state institutions, including the judiciary, that his aim is to modernise a creaking system and not to accumulate power, and that his changes comply with European rules.
He says criticism of his reforms is part of a campaign against him mounted by political opponents and business interests looking for a pretext to oust him from office. (Additional reporting by Krisztina Than in Budapest; Writing by Christian Lowe; Editing by Mark Heinrich)