'Car bomb' outside ACL driven by suicide

Federal police believe the man involved in car explosion outside an Australian Christian Lobby office was trying to kill himself.

The van - stocked with gas cylinders - ignited in the car park of the Canberra building in late December, blowing out windows and destroying furniture.

The driver is still receiving medical treatment for both injuries sustained during the incident and for mental illness.

Australian Federal Police Commissioner Andrew Colvin said the man remained unfit to speak to officers, but was confident his primary motivation was suicide.

"We do believe he knew it was the Australian Christian Lobby, but he was not driven by a motivation or an ideology based on anything the Christian Lobby had done or said," he told a Senate estimates committee on Tuesday.

"His motivation was driven by mental illness and his desire to commit suicide."

But the lobby's managing director, Lyle Shelton, refused to believe the assessment.

"Can't believe what I've just heard from the AFP in Senate Estimates. The alleged bomber knew he was targeting our office," he tweeted.

The matter is still being investigated.

Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.

Suicide Call Back Service 1300 659 467.

MensLine Australia 1300 78 99 78.