Concentration camp

Concentration camps, also referred to as labour camps (TV: Turn Left), re-education camps (PROSE: Revolution Man) or, more bluntly, death camps, (TV: The Middle Men) were facilities used by totalitarian regimes such as the Nazis (PROSE: Timewyrm: Exodus) and communists (PROSE: Revolution Man) to imprison or exterminate individuals they considered to be undesirables.

Use by the Nazis
The Seventh Doctor said for the Nazis the "undesirables" included Jews, homosexuals, Gypsies and trade unionists — "anyone a bit different, anyone they don't like the look of." (PROSE: Timewyrm: Exodus) According to Jason Kane, the prisoners were used as slave labour, expected to survive with only scraps of food and clothing. (AUDIO: Just War) Most died. (PROSE: Timewyrm: Exodus)

In 1903, after receiving a wealth of information from the future, Grigori Rasputin foresaw the Holocaust. (AUDIO: The Wanderer)

In May 1940, a submarine carrying Zyklon B gas to a concentration camp was attacked by a Nemonite. (AUDIO: The Nemonite Invasion)

Fitz Kreiner's uncle, Jürgen Kreiner, was among those sent to concentration camps during World War II. As a result of his internment, Jürgen's arms bore the marks of a serial number, the meaning of which Otto Kreiner was reluctant to explain to his young son, Fitz. (PROSE: Frontier Worlds)

Use by other regimes
In Maoist China a system of camps existed to "re-educate" citizens whose patterns of thought were considered out of line with the government's ideology. (PROSE: Revolution Man)

In the aftermath of Miracle Day in 2011, in which people ceased to die, people were taken to overflow camps. Category ones, people who would have died had it not been for Miracle Day, were taken to Modules and incinerated. (TV: The Categories of Life) Gwen Cooper compared these camps to concentration camps. (TV: The Middle Men)

Alternate timelines and parallel universes
In another alternative timeline accidentally created by the Seventh Doctor and Ace's arrival in Colditz Castle in October 1944, an alternative version of the Eighth Doctor who used the name "Johann Schmidt" disrupted the Nazi's "ethnic cleansing programmes" between 1955 and 1965. Consequently, he attracted the attention of the Nazi authorities but nevertheless maintained his liberty. (AUDIO: Klein's Story)

In a parallel world, in the aftermath of the destruction of London, among other disasters caused by aliens, foreigners in Britain were taken to labour camps in 2009, as other countries closed off their borders. Upon hearing this, Wilfred Mott exclaimed, "That's what they called them last time!" (TV: Turn Left) alluding to the real-world concentration camps established by the British and the Americans during the Second World War where foreign nationals and even citizens of foreign descent (particularly the Japanese) were imprisoned without charge or trial.

On the Inferno Earth a system of labour camps existed in Great Britain to punish citizens sentenced by the People's Court for political crimes, including advocacy of liberal or free-market values, unlawful political demonstrations, (TV: Inferno), racketeering, (PROSE: I, Alastair) and importing seditious literature. (PROSE: Still Lives) Even when the sentence passed in court was not death prisoners deemed unrehabilitated and considered particularly politically dangerous were sometimes killed once they were no longer useful, with their deaths officially ruled as accidents or failed escape attempts. Prisoners merely considered to be eccentrics rather than actually dangerous to the regime were usually released after a few years. (TV: Inferno)