Quisling

Quisling was an epithet roughly meaning "a traitor who collaborates with the enemy". The Third Doctor once called the Controller a quisling. When he discovered that the Controller was the third Controller in his family line, the Doctor said that the Controller was from a "family of quislings". (TV: Day of the Daleks)

George Ratcliffe was designated a quisling after he spoke out against Britain's involvement in World War II, advocating an alliance with Nazi Germany. By November 1963, he was still designated as such by the Renegade Daleks' battle computer. (PROSE: Remembrance of the Daleks)

Behind the scenes
In the real world, "Quisling" is derived from the Norwegian politician, Vidkun Quisling, who ruled Norway for the Germans during World War II.