KUALA LUMPUR, MALAYSIA - A Malaysian opposition politician was charged with sedition on Monday over a blog posting that allegedly insulted the royal ruler of central Selangor state, his lawyer said.

State assemblyman Shuhaimi Shafiei was charged over a December blog posting that prosecutors claimed questioned the powers of Sultan Sharafuddin Idris Shah, his lawyer Amer Hamzah Arshad said.

The allegation stems from a row over the appointment of a new chief civil servant in Selangor which was bitterly opposed by the opposition - which rules Malaysia's richest state - but received the sultan's assent.

"Suhaimi has pleaded not guilty to the sedition charge and we also informed the judge that we would be filing a motion with the High Court challenging the constitutionality of the Sedition Act," he told AFP.

Amer said that the law was introduced during the British colonial era but had only been used after the country's independence in 1957, to silence the opposition and civil society groups.

"The Sedition Act should not be used, it is outdated and has no place in our society. We should deal with the facts and debate the legal arguments rather than spreading fear through the selective application of this act," he said.

Amer said Suhaimi could face three years in jail and possibly lose his seat in the state assembly if convicted.

Malaysian authorities justify the use of the legislation as being vital to to curb comments or actions that could stoke racial conflict in the multicultural nation.

Last month, the government announced plans for a national roadshow to defend the strict sedition and media control laws that have been criticised as tools to stifle dissent.

The opposition alliance seized power in Selangor and four other states in 2008 elections which yielded its best ever result, stunning the coalition which has ruled Malaysia for half a century.