PHNOM PENH - Cambodia on Friday banned the denial of atrocities committed by the Khmer Rouge regime with a new law, a move the opposition claims is a political attack weeks ahead of national polls.

The law bans statements denying crimes by the communist regime that ruled from 1975-79 killing an estimated two million people, and carries a sentence of up to two years in jail.

The law, similar to legislation covering Holocaust denial in Germany and France, was proposed by strongman Prime Minister Hun Sen after a recording emerged of an opposition leader apparently excusing the Khmer Rouge from responsibility for running a notorious torture prison during their rule. Around 15,000 men, women and children were tortured and executed at the prison, also known as S-21, in central Phnom Penh.

Kem Sokha has admitted it is his voice on the recording but alleges it was edited to say the contentious comments, a claim backed by the CNRP which alleges the tape was aired "to cause political trouble" ahead of a general election in July.

Lawmakers, mostly from the ruling party, unanimously approved the law -- which has only five articles -- after around an hour of debate on Friday.

The law will prosecute anyone who "does not acknowledge, denies or diminishes... crimes committed under the Democratic Kampuchea", the draft said, referring to the brutal regime's official name.

Lawmaker Cheam Yeap told parliament that denial of the crimes committed by the Khmer Rouge was "a serious insult to the souls" of those who died under its rule.

The CNRP said it was "very disappointed" that the ruling party and parliament had rushed through the legislation, adding the law should also ban former Khmer Rouge leaders from senior office.

Hun Sen and several other top officials were Khmer Rouge cadres.

Critics also say the law may jeopardise painstaking efforts to heal the country.

"You don't need the law to protect the truth of what happened during the Khmer Rouge," Youk Chhang, director of the Documentation Centre of Cambodia which researches Khmer Rouge atrocities, told AFP.

Hun Sen has repeatedly warned that the country risks civil war and even a return to the ruthless regime if the opposition wins polls.

"Chaos will surely happen if they really win.... I would like to send a message out that Pol Pot's regime will return," he said last month.

The CNRP has only a slim chance of gaining enough votes to oust Hun Sen, who has ruled the country since 1985.

Led by "Brother Number One" Pol Pot, who died in 1998, the Khmer Rouge from 1975-79 wiped out nearly a quarter of Cambodia's population through starvation, overwork or execution in a bid to create an agrarian utopia.