DECRIMINALISING drugs will be investigated by Australia's top independent policy adviser under a plan championed by a trio of federal MPs from different sides of Parliament, with the aim to take politics out of the debate.

In April a report from the Australia21 think tank argued the ''war on drugs'' and tough stance on illegal substances had failed, sparking debate and gaining support for decriminalising personal use from eminent Australians, including former police commissioners and premiers.

Liberal MP Mal Washer, Greens senator Richard Di Natale (who are both doctors) and independent Rob Oakeshott will this morning call on the government to ask the Productivity Commission to investigate the current adequacy of illegal drug laws.

''The reason for the Productivity Commission is to take the politics out of it and base it on evidence - which is dispassionate and hard nosed,'' Senator Di Natale told The Age. ''I've lost count of how many MPs have told me privately we have to change the approach to drugs but won't speak out.''

It is unclear which MP would move a motion but Dr Washer said he would ideally like a government MP to do so to ensure the best chance of success.