PNHOM PENH: Cambodian Prime Minister Hun Sen on Saturday called on lawmakers from the main opposition party to defect ahead of a court ruling on whether to dissolve it, saying they could be banned from politics for five years if they left it too late.

The government's move to ban the Cambodia National Rescue Party (CNRP) follows the arrest of its leader, Kem Sokha, on treason charges.

He rejects the charges as politically motivated ahead of next year's general election.

Hun Sen, the world's longest serving prime minister, has held power for more than 32 years.

Western countries have called for the release of Kem Sokha and for an end to attempts to dissolve the CNRP.

Hun Sen said in a message to CNRP parliamentarians and local councillors, he knew not all had been involved in Kem Sokha's alleged treason and they should take the chance to switch to his ruling Cambodian People's Party (CPP).

"I want to give you this opportunity to continue in your job," he said. "It will not only be that the party is dissolved and then the matter is finished. Maybe more than 100 people will be banned from politics for five years."

He said such a ban was likely to include all the CNRP's steering committee - meaning most of its members of parliament, around half of whom have fled Cambodia to escape arrest.

No CNRP officials were immediately available for comment.

Cambodia's Supreme Court is in theory independent of the government in ruling on the interior ministry's request for the CNRP to be banned, but Hun Sen has said it is "a fact" that the party will be dissolved.

Cambodia's parliament has already passed a law to share out elected positions to other parties if the CNRP is dissolved. Most of the seats in parliament will go to minor parties while local councils, known as communes, will be taken over by the ruling party.