A legal brief has been sent to the International Criminal Court (ICC) alleging former prime minister John Howard committed a war crime by sending troops to Iraq.

A loose alliance of peace activists, lawyers, academics and politicians is behind the brief, organised by the ICC Action group in Melbourne.

Organiser Glen Floyd says Mr Howard should be held accountable for sending troops to a war not sanctioned by the United Nations.

"We have produced a 52-page brief of evidence which states to the chief prosecutor of the criminal court that we allege John Howard's actions are war crimes under article 8 of the Rome Statute," he said.

Democrats Senator Lyn Allison says the legal brief sent to the ICC is justified.

Senator Allison, who is one of several eminent people supporting the move, says accountability is important.

"This action has been taken to hold those accountable for their action, so it's essentially our prime minister - he was the one at the time [who] was the executive of government, made the decision," she said.

'It wasn't put to the Parliament and as we all know, it turned out to be unjustified."

A similar brief has been sent by a group from the United Kingdom regarding former prime minister Tony Blair. The United States is not a signatory to the court.