Yazidi and Christian women slaves are being sold for as little as £27, a document issued by ISIS reveals.

Obtained by IraqiNews.com, the document sets out guidelines for the price of women and children and says that anyone violating these controls will be executed.

"The market to sell women and spoils of war has been experiencing a significant decrease, which has adversely affected ISIS revenue and financing of the Mujahideen," it reads.

Individuals are forbidden from purchasing more than three slaves, unless they are from foreign countries such as Turkey or Syria.

The price list reveals that a Yazidi or Christian woman between 40 and 50 years old will fetch 50,000 dinars, or around £27.

The price of a slave increases as they get younger; a girl between 10 and 20 years old will sell for about £80, while those between the ages of one and nine are sold for just over £100.

A video recently emerged apparently showing ISIS fighters discussing the price of Yazidi women and girls during a "slave market day" in Mosul.

"Today is distribution day, God willing. Each one takes his share," a man says to the camera.

Several men are seen bartering over the women, with one offering a pistol in exchange for a girl, while another says the price is dependent on "how she looks".

ISIS has admitted to selling women to their fighters and justified the practice with early Islamic teachings.

Tearfund's Katie Harrison, who spent time in Iraq earlier this year, told Christian Today that she heard about the "systematic rounding up of women and girls" from a number of people in the region.

She described "the rapid, enforced divorce of married women from their husbands; the 'testing' of single women to assess whether they're considered to be a virgin; the colour-coding by clothing of married and single women; the selling in an open market with virgins commanding the highest price; and the hasty marriage ceremonies between buyer and the woman they've bought in order to justify his raping her."

"And these are not just grown women," Harrison said. "The youngest girl we heard of being taken for rape was three years old."