Several cabinet ministers have persuaded the cabinet against making firefighter Muhammad Adib Mohd Kassim's post-mortem report public.

This was alleged by Umno supreme council member Lokman Noor Adam during a protest against the federal government tonight for failing to act against Adib's alleged murderers.

"Some of these cabinet ministers, among others P Waythamoorthy, have urged cabinet to tamper with the post-mortem report.

"(They wanted the report to state) that Adib died because of an accident, that he was hit by a vehicle. Are we going to let this happen?" he asked the 100 people present.

Lokman pointed out previous statements by the authorities had already stated that Adib was assaulted and that four individuals were being investigated for murder.

He told the crowd that he had no quarrel with the police but instead was training his guns on attorney-general Tommy Thomas, Home Minister Muhyiddin Yassin and Prime Minister Dr Mahathir Mohamad for allegedly "protecting" Adib's alleged murderers.

When asked for clarification later, Lokman told reporters that apart from Waythamoorthy, he was informed that several "Indian ministers" were involved in the alleged cover-up plot.

"They are of the opinion that if the report said Adib was killed because of an assault, it would result in racial riots.

"Malaysians, especially the Malays, are rational people. We don't simply riot. There are four perpetrators […] they should be charged in court," he said.

Lokman also urged the federal government to be brave and make the post-mortem report public.