Don't believe there is one, nor do I believe there's such thing as a "perfect" form of any government in practicality. The problem isn't with any particular system, though. The problem is simply that the notion of any form of government naturally clashes with the human condition. If there's a ruling body, there's someone who wants to overthrow it. If there's power, there's someone who wants to horde or abuse it. Theoretically, any form of government can be perfect...on paper, but that all goes tits up when the reality of the situation kicks in.