KUALA LUMPUR (AFP) - A top Malaysian opposition MP was jailed for one month on Friday (Sept 29) after he withdrew an appeal for a "petty" offence that his lawyer said highlighted the "absurdity" of the government.

Chua Tian Chang, better known as Tian Chua, had appealed the sentence handed to him in January 2014 after he was found guilty of trespassing for refusing to leave a restricted police training centre in 2012.

Chua, 53, is vice-president of the opposition Parti Keadilan Rakyat (PKR) and his jailing comes just months ahead of elections due to be called by August 2018 in which a fractious opposition coalition faces a strong challenge in its attempt to topple Prime Minister Najib Razak.

The 2012 incident saw Chua and hundreds of others detained at the Police Training Centre during massive protests in which thousands marched in the capital to demand sweeping electoral reforms.

Chua was released but refused to leave the centre as he wanted to make sure the other protesters detained there were all right, according to his lawyer, Ms Latheefa Koya.

Ms Latheefa told AFP the politician regards withdrawing his appeal as "a small price to pay for a bigger cause".

"This would definitely highlight the absurdity of the authorities... to charge someone for such a petty matter," she said.

Chua pulled out of the appeal because "he is not afraid of jail", Ms Latheefa added.

The politician also has a number of other offences under appeal, including a three-month jail sentence for sedition, Mr N. Surendran, another of his lawyers, said.

He will however remain an MP as the jail term and fine he received of 1,000 ringgit (S$321.47) is below the threshold for disqualification under Malaysian law.

The PKR was founded by jailed opposition leader Anwar Ibrahim. It is currently led by Anwar's wife, Dr Wan Azizah Wan Ismail, and is one of four parties in an opposition coalition aiming to unseat Mr Najib at the polls.

Mr Najib, who has weathered a corruption scandal, is due to call elections by next year, although there has been speculation it could be sooner.