Opposition leader Adrian Delia accused the Prime Minister of a "dictatorial" attack against a Nationalist MP over a criminal complaint filed against the Armed Forces.
In a televised address on Saturday evening, Delia staunchly denied that the Opposition was behind two criminal complaints filed by the NGO Repubblika over the government's refusal to rescue migrants stranded at sea and over the alleged intentional sabotage by army personnel of a vessel carrying asylum seekers.
However, he supported the investigation into what he described as "very serious accusations".
The criminal complaints were filed on the NGO's behalf by four lawyers including Opposition MP Jason Azzopardi.
Prime Minister Robert Abela, flanked by the entire cabinet, laid into Azzopardi and the NGO on Friday, saying he was being accused of murder and that there were some there were some who wanted him, the AFM brigadier, and other army personnel to spend their lives in prison.
Delia on Saturday insisted that the reports were not filed in the Opposition's name, and that Azzopardi was acting in his professional capacity as a lawyer for the NGO.
"It is unacceptable in a democratic society for these sort of attacks to be made against lawyers, whoever they may be, acting in the name of their clients," Delia said.
"These things happen only in dictatorial countries and the Prime Minister fell far short of carrying out his duties when he behaved in the manner he did yesterday."
He insisted that sitting MPs with legal practices - of whom there are many - had every right to carry out their work without interference, although he said the Nationalist Party was open to discussing guidelines for how MPs should conduct themselves in such situations.
Delia said the government had yet to deny the allegations, as it would have been expected to do in Friday's address.
He accused the Prime Minister of attempting to politicise serious accusations that included the deaths of several people and which would merit an investigation in any country.
The Prime Minister, he said, had only spoken out when he realised he would face investigation.
"Our position is clear: we can never allow any life to be lost. If we did, we would be ashamed to say we were human," he said.
"At the same time, I want to make clear that those who do not qualify for asylum should be immediately sent back to their countries, and those who do should be distributed fairly among all European countries."