Leftist opposition parties submitted a censure motion against the conservative government this week accusing it of "trying to hide the truth" after a freight train collided head-on with a passenger train in central Greece, the worst accident in the country's history.

The government denies wrongdoing and is expected to survive the vote given its party's majority. But the motion highlights how many are still angered by a disaster that revealed how decades of neglect and mismanagement had jeopardised railway safety. Experts say little has changed to improve standards since.

"Like every Greek citizen, we want to know the truth," Nikos Androulakis, the head of the centre-left PASOK party, told parliament on Wednesday.

A judicial investigation is underway and is expected to be completed in the coming months. Authorities have charged dozens of people over the crash, including a station master who is in custody pending trial.

To Vima newspaper reported on Saturday that a recording of a dialogue between the station master and the train driver, leaked to media hours after the crash, had been allegedly edited to put the blame on human error rather than systemic problems in the rail network.

Reuters was unable to verify the allegations.

Investigators hired by victims' relatives have also alleged that quickly removing burnt carriages from the crash site and laying down gravel may have destroyed evidence. Greece did not have a functional national investigating body of such incidents at the time of the crash.

Victims' relatives have started a petition to amend century old rules that protect politicians from prosecution. They have collected more than 1.3 million signatures so far.

Mitsotakis' New Democracy party, which leads opinion polls, says the opposition is exploiting the case to benefit politically. Justice Minister George Floridis called the allegations a "campaign of lies and deception".