A top Sri Lankan government official has accused aid group Action Contre la Faim of being responsible for the massacre of 17 of their own local staff last year through "negligence" and "irresponsibility".

Rajiva Wijesinha, head of the government's peace secretariat and in charge of coordinating the island's battered peace process for the state, has written to the island's Human Rights Minister calling for an independent probe into the matter.

Nordic truce monitors have blamed the massacre, the worst attack on aid workers since the 2003 bomb attack on the United Nations office in Baghdad, on state security forces. The government denies this and says it is investigating.

"We have not dealt firmly enough with the original reason for the tragedy, which was the utter irresponsibility of the ACF organisation in putting such workers at risk," Wijesinha wrote in a letter to Human Rights Minister Mahinda Samarasinghe dated August 13, his office said.

Wijesinha said the government should insist on an independent probe into why the group's staff were told to stay put in their compound during fighting between troops and Tamil Tiger rebels and demand more compensation for the families of the victims.

"There is no doubt that such negligence, if addressed in a European court of law, would have resulted in the award of massive damages to the grieved families, rather than the puny amounts that I gather from NGO sources have been awarded," he added.

President Mahinda Rajapaksa's government denies security forces have been involved in rights abuses and says a presidential commission is probing the allegations. The government has also rejected calls for a United Nations rights monitoring mission.

International observers say the presidential inquiry into the massacre fails to meet international standards, and Action Contre la Faim is still waiting for answers as to who killed its staff a year on.

"If they want an inquiry, ACF agrees to cooperate, as long as it is an international and independent inquiry," said Loan Tran-Thanh, head of ACF's Sri Lanka mission.

"The main point is we shouldn't forget our focus, which is who did the killing and who held the weapons."

U.N. Under-Secretary-General for Humanitarian Affairs John Holmes said on a visit to Sri Lanka last week the island had one of the worst records in the world for humanitarian aid worker safety.

He said almost 30 aid workers had been killed over the past 18 months. The Consortium for Humanitarian Agencies, an umbrella group of 104 aid agencies operating in Sri Lanka, puts the number at 34, which the government questions.

The government has vilified Holmes, accusing him of bias, helping to tarnish the government's reputation and indiscretion.

Press freedom groups say Sri Lanka is also among the most dangerous places in the world to cover. Rights groups say around a dozen journalists and media workers have been killed since late 2005.

Nearly 70,000 people have been killed in the conflict in Sri Lanka since 1983 -- around 4,500 in the last year alone.