Thailand's government is facing a no-confidence vote in parliament over the violence which ended lengthy political protests in the capital, Bangkok.
Prime Minister Abhisit Vejjajiva appears confident of surviving the censure, as his coalition allies have said they will not desert him.
The 19 May crackdown, which followed days of skirmishes, left more than 80 people dead and 1,800 injured.
On Monday, a senior UN official called for an independent inquiry to be held.
UN High Commissioner for Human Rights Navi Pillay urged the government to "ensure that an independent investigation of recent events be conducted, and all those found responsible for human-rights violations are held to account".
The government will face a vote on its conduct on Wednesday following two days of intense debate which has focused on the conduct of troops during the operation.
Opposition politicians have taken it in turns to denounce the government for its decision to send in the army to break up the two-month long political protest which paralysed parts of Bangkok.
They say that the majority of the victims were unarmed demonstrators, proof that the soldiers were guilty of using disproportionate force.
But Deputy Premier Suthep Thaugsuban said video footage of the violence in the capital showed the government was not to blame for the deaths of protesters.
"In the past two days your aim has been to make people believe that the prime minister and I ordered the military to kill people," he said.
"Your allegations are extremely unfair to those soldiers."
'Can't hide the sky'
The controversial deaths of six people in a temple during the forced ending to the anti-government "red-shirt" rally has dominated the debate.
Thai and foreign journalists, among other observers on the scene, say soldiers fired into the grounds of Wat Pathum Wanaram from the elevated commuter train nearby. The government has issued various denials.
Six people - including one local Red Cross nurse - were found dead inside the grounds of the temple, where red-shirt protesters had taken refuge from the fire-fights going on during the day.
"What happened at Wat Pathum cannot be ignored," said Jatuporn Prompan- a red-shirt leader and MP in the opposition Puea Thai party - who headlined the debate.
"You can't hide the sky with your palm. The truth must come out."
The government says it only turned to the military as a last resort after all attempts to negotiate a peaceful resolution to the crisis failed.
It also points to the presence of gunmen among the protesters as justification for the use of live ammunition.
Mr Abhisit said he had no concerns about rebutting the charges levelled at him during the debate but claimed that distorted views of the opposition lawmakers might hinder national reconciliation.
"There are attempts to pass the blame on violence and this will make it more difficult for reconciliation to materialise," he said.
The government has promised an independent investigation into all incidents of violence but has rejected the idea of international assistance.
Mr Abhisit said he would not interfere with any investigation and that "whatever the outcome," he and Mr Suthep were "ready to accept it", the AFP news agency reports.
But the BBC's Rachel Harvey in Bangkok says that opposition politicians, many of whom actively supported the protests, are suspicious that any government-appointed panel will not be impartial.
The governing coalition has a majority in parliament and is thought likely to win the no-confidence vote.
But under the current state of emergency, state media is being strictly controlled and opposition media has been largely shut down. So this debate is, in effect, the first public airing of the bitter arguments polarising Thai society, our correspondent says.
Several opposition figures have made a point of highlighting the government's censorship of the media and its recent closure of a large number of blogs, websites and broadcasts under the continuing state of emergency rule.
They have also complained about a poor signal and frequent interruption of the live broadcast of the censure debate.
The Erawan Emergency Centre in Bangkok says 87 have now died as a result of the violence since 14 May - the majority were civilians. A total of 1,406 civilians and security personel were also injured.
The red-shirts had been protesting in Bangkok since 14 March, occupying the shopping district and forcing hotels and shops to close.
On 19 May, the government moved in to seal off the area and a renegade general who backed the protests was shot dead.
The red-shirts are a loose coalition of left-wing activists, democracy campaigners and mainly rural supporters of Mr Thaksin.
They are demanding fresh polls because they say the government - which came to power through a parliamentary deal rather than an election - is illegitimate.