Jakarta – Human Rights Watch on Saturday slammed Indonesia's MPs for passing a law that could let former president Suharto and senior military officers escape punishment for gross human rights abuses, including those in East Timor.

In a statement received here, the global rights body said the ruling "makes it far less likely that former president Suharto or any army officer could be charged with crimes against humanity."

The constititional amendment passed by the 700-member People's Consultative Assembly (MPR) on Friday would also protect Suharto and the officers from prosecution for "any atrocities committed by Indonesian troops from 1965," it said

The amendment invokes the principle of non-retroactivity – "meaning that no one could be charged with a crime that did not constitute an offence in law at the time it was committed," Human Rights Watch said.

The statement, entitled: "Lawmakers let perpetrators off the hook", said that as Indonesia did not yet have a human rights law "the most serious charge that anyone involved in the scorched-earth campaign in East Timor or the atrocities in Aceh could face is murder."

"Crimes against humanity are so serious that non-retroactivity doesn't usually apply to them," the organization quoted Rights Watch Asia director Sidney Jones as saying. "This is the prevailing trend and Indonesian judges should go along with it."

The new constitutional amendment – Amendment 28 (I) – could mean that the "masterminds of the 1999 violence in East Timor will be judged less harshly than rank and file militia members," it said.

East Timor was devastated by Indonesian military-backed militia in retaliation for its vote for independence from Indonesia on August 30 last year, prompting the United Nations to dispatch an international force to quell the violence.

In Jakarta on Friday Indonesia's Attorney General Marzuki Darusman told the press that the trials of those suspected of masterminding the Timor violence would go ahead anyway.

"It can be guaranteed that current investigations into human rights violations in East Timor and several other cases will be exempt from the amended article 28 in relation to its clause on retroactivity," Darusman told journalists.

Darusman said his guarantee that prosecutions could go ahead was based on information from the leader of the assembly commission which debated the constitutional amendments.

"[The commission leader] said that the people who put forward that amendment had no intention of erasing anything to do with the planned human rights tribunal [for East Timor]," Darusman said. "So in principle the human rights tribunal on East Timor can still take place."

Former Indonesian armed forces chief General Wiranto is among those named by a preliminary Indonesian probe into the East Timor violence, which left at least 600 dead, whole towns razed and more than 200,0000 people forced out of the territory.

But Rights Watch said that "if and when" Darusman succeeds in bringing any senior officers to trial, they would be tried "for the common crime of murder" – in short under the existing criminal code.

Rights Watch urged the MPR in its next annual session to uphold the right of the judiciary to set up ad hoc courts which would not be bound by the retroactive principle to try gross human rights abuses.

UN Human Rights Commissioner Mary Robinson, speaking after a meeting with Darusman here last week, warned again that the UN would unilaterally call an international war crimes tribunal if Jakarta failed to bring the perpetrators of the Timor violence to trial.