The United Planets was a government which existed at some point after humans became a regularly space-faring species. It bound together peoples from different planets opposed to the Daleks and was the authorising body for the Anti-Dalek Force. It was led by a president, who was the head of the United Planets Parliament — thus suggesting a parliamentary form of democracy. It was based on Earth. (DAN: Terry Nation's Dalek Annuals 1976 - 1979)
At one point, its president was Cal Tarrant. (PROSE: The Doomsday Machine) The ADF were under his direct control, as evidenced by an extant communiqué from Space Major Joel Shaw which requested orders from Tarrant. (DAN: Special Report)
Behind the scenes
The United Planets was a regular feature of the latter group of Dalek annuals, and were often seen to be giving orders to either Reb Shavron, Mark Seven or Joel Shaw, the three most regular characters of those annuals.