PHNOM PENH (REUTERS) - Cambodian government lawyers filed a lawsuit on Friday (Oct 6) to demand the dissolution of Cambodia's main opposition party after its leader was charged with treason last month.

The arrest of Kem Sokha on Sept 3 brought condemnation from Western countries, while his Cambodia National Rescue Party (CNRP) said it was a ploy by Prime Minister Hun Sen to win an election next year and keep his three-decade hold on power.

Lawyers for the government said the opposition had conspired with foreigners to topple the government, citing a 2013 video clip that shows Kem Sokha talking about a plan to take power with the help of Americans.

The CNRP is in tatters, with more than 20 MPs skipping abroad in the past month after their stand-in leader Kem Sokha was locked up in a remote prison on dubious treason charges.

His arrest comes months after a series of legal convictions and new laws forced the party's long-time frontman Sam Rainsy to step down.

Many civil society groups railing against corruption and repression have also been shut down or sidelined by court cases.