India's top court ruled Wednesday that lawmakers should be thrown out of office if they are convicted of a serious crime, a judgement hailed as a major step towards cleaning up the political system.

The Supreme Court said state and federal lawmakers will be forced to quit politics and will be barred from contesting future elections if they are convicted of a crime that carries a sentence of at least two years in jail.

"If a person has no right to vote (if convicted of a crime), he has no right to contest," Judges A.K Patnaik and S.J Mukhopadhyay ruled.

Some 160 lawmakers from various parties in the national lower house of parliament are facing a range of criminal charges and more than 1,400 politicians from state legislatures, according to campaign group the Association for Democratic Reforms.

"This is a milestone for Indian politics. If you are convicted of a crime from now on, you don't have the right to be in politics," said the association's national coordinator Anil Bairwal.

"It's a significant step towards cleaning up politics," Bairwal, who was in court to hear the decision, told AFP.

The ruling comes as Prime Minister Manmohan Singh's government has been rocked by a series of graft scandals involving mobile phone licences, coalfields and the Commonwealth Games in New Delhi among other issues.

Millions of people took to the streets in cities across India last year to protest at the scandals amid seething anger at perceived endemic corruption in politics and the wider public sector.

The ruling could have a significant impact ahead of state and national elections which are due by May next year, Bairwal said.

The court ruled that politicians convicted of a crime in future could no longer remain in office by pointing to their appeal against the conviction, a process that can take years in India's notoriously slow and backlogged legal system.

Their disqualification from office "takes place from the date of conviction", the judges said, adding that the ruling only applied to future convictions.

The ruling followed a petition from several activists challenging legislation called the Representation of the People Act, which allowed politicians to stay in office pending their appeals.

Politicians currently face a range of criminal charges from rape to kidnapping and corruption, according to the association.

In one of the most high profile cases, a former telecom minister is currently on trial over the sale of second-generation (2G) telecoms licences at far below their commercial value to selected companies. He quit in 2010 over the scandal.

A former top leader of India's main opposition Hindu nationalist party was jailed in 2012 for four years for accepting a bribe in a fake arms deal that was a media sting operation.