Kim Joo-il escaped his job as an Army captain in 2007 and now lives in Britain campaigning against the brutal Kim Jong Un dictatorship.
In an exclusive interview at the launch of a new report into human rights abuses in North Korea he said: "If you are caught practicing religion by yourself then you're sent to prison camps - no question.
"If you're found to have contacted outside churches or missionaries then you are executed publically."
The All Party Parliamentary Group for International Freedom of Religion or Belief (APPG) has been researching persecution in North Korea.
It found the mistreatment of religious groups is well-known. Of all the refugees interviewed by the Database Centre for North Korean Human Rights, 99.7% said that there is no religious freedom in North Korea. Many religious people get caught when they try to escape the country - often they're found in China.
The report makes a number of recommendations to the British Government, including:
- Pursue the UN Commission of Inquiry's recommendation of referral to the International Criminal Court;
- Thoroughly consider and instigate appropriate alternative justice mechanisms to compliment the International Criminal Court process;
- Ensure that all discussions on the North Korea at the UN and the EU include human rights and especially the 'orphaned right' of freedom of religion and belief: Article 18.
- Continue to critically engage with North Korea bilaterally on human rights with the UK's Ambassador in Pyongyang elevating religious freedom to a high priority;
- Pursue creative ways of breaking the information blockade, for example through the use of DVDs, mobile phones and USBs;
- To fund or otherwise facilitate further research into the human rights situation in the DPRK, especially on the possibility that genocide has been perpetrated against Christians;
Baroness Berridge, chairman of the APPG, said: "For the past sixty-plus years, the Democratic People's Republic of North Korea has committed egregious human rights violations - the details of which would turn the stomach of even the most hardened person.
"This includes banishing those who follow a religion to remote places, incarcerating them, subjecting them to torture in labour camps, and murdering Christians for merely possessing a Bible.
"For many years North Korea has been viewed as an impossible case, but now the international community is finally beginning to afford the country the attention its people so desperately need."
Listen to a translated interview with Kim Joo-il:
Listen to Geoffrey Clifton-Brown MP and vice-chair of the North Korea All-Party Parliamentary Group: