A British civic group claims that as many as one million political prisoners may have been killed in North Korean concentration camps.

The Britain-based Christian Solidarity Worldwide (CSW) cited interviews it conducted over the past seven years with North Korean refugees who escaped from the North’s gulags.

A CSW report said that, considering that about five to ten percent of the detainees die in a political prison and factoring in the North's severe famines, the number of deaths should be somewhere between 380-thousand to one million.

The Christian group previously had arranged for North Korean escapees Ahn Myong-chol and Sin Dong-hyok to testify before Britain's opposition Conservative Party chief David Cameron and other parliamentarians in a committee on the North Korean issue.