He said the drawn-out military police inquiries into scores of alleged abuse and murder cases - which have taken up to 21 months to complete - has severely damaged army morale.
"One of the tenets of military justice is that it should be swift and that people should not be left hanging," he said. "But they just write it down and then throw it away."
Lt Col Collins became famous in March 2003 for a stirring eve-of-battle address to his Royal Irish Regiment troops. But he was later investigated over claims by a US army major that he had abused Iraqi prisoners - claims which were dropped after an eight-month inquiry. He has since left the Army.
Lt Col Collins said the Royal Military Police and plainclothes Special Investigation Branch should be replaced by a better-resourced, professional service which is fully independent of the military. "It's all deeply confused, and does not keep pace with modern life. It is harming the reputation of the British Army," he said.
His proposals echo similar demands from High Court judges, MPs and human rights groups, who allege the Army has failed to investigate effectively a series of suspicious shootings and abuse cases because the Military Police are too closely linked to the armed forces. However, Lt Col Collins rejected moves to strip commanding officers of their controversial powers to dictate whether a soldier should be investigated or charged. Only commanders on the ground could accurately weigh up whether a soldier's actions were justified, he said.
The MoD stopped commanders in Iraq from using these powers in February last year on the advice of the Attorney General, Lord Goldsmith. It emerged that one CO had blocked a decision to court martial one of his troops - a decision later over-ruled by Lord Goldsmith.
Meanwhile, an Independent on Sunday investigation has found that less than a third of British military personnel in Iraq were given a crucial booklet on the "rules of war" despite ministerial claims that it was issued to 65,000 troops.
Only 20,000 copies of the eight-page handbook were printed, leading to accusations that the MoD failed to properly instruct British troops how to treat prisoners and Iraqi civilians fairly and humanely. The MoD has denied this, claiming the booklet was only a reminder.Reuse content