Ex-Guantanamo detainee Mamdouh Habib says he could have brought bloodless end to Martin Place siege

Wrongly-accused Guantanamo Bay inmate Mamdouh Habib says he could have stopped the Martin Place siege without casualties and that gunman Man Monis was "not violent" and never intended to kill anybody.

Mr Habib was wrongly accused of being an "enemy combatant" by the US and held for three years in a number of locations including Guantanamo Bay.

He was released without charge in 2005 and in 2010 received a payout from the Australian government after an Egyptian intelligence officer confirmed an Australian official had been present when Mr Habib was tortured on at least one occasion.

Mr Habib unsuccessfully ran as an independent for the state NSW seat of Auburn in 2007, when Monis helped him campaign.

Now Mr Habib has come forward to say he offered to negotiate with Monis during the siege, Fairfax Media has reported.

He said he was "100 per cent" certain he could have ended the hostage situation without bloodshed.

Police rejected a number of offers from Muslim leaders and community members to speak with Monis, not wanting to expose untrained civilians to the precarious situation.

He said he believed Monis was "disturbed" and had claimed to be undertaking a terrorist attack to draw as much attention as possible.

However, Mr Habib said Monis' true reasons for his lethal actions were other grievances with the government and with the family court system, which had forbidden him from seeing his two children.

At the time of the siege, Monis was facing charges of being an accessory to the murder of his ex-wife, and dozens of sexual assaults.

The self-proclaimed sheikh and two hostages were killed in the final moments of the 16-hour Martin Place siege.