This comes as US President Donald Trump announced in his State of the Union Speech on Tuesday that he will be meeting the secretive state's leader this month about the country's nuclear weapons programme.
Trump told the media that he raised human rights abuses in private with Kim Jong-un during their historic summit in June 2018 and it was hoped by many that this would result in Christians there being treated better.
However, local sources have told Open Doors that there are many signs that persecution is actually getting worse.
They claim there has been an increased number of arrests and abductions of South Korean and Chinese Korean Christians and missionaries in China.
They said border control has been tightened, harsher punishments have been introduced for North Korean citizens who are repatriated from China, and there has been an increased effort by the North Korean government to eliminate Christian evangelism.
Joo Eun, a North Korean who now lives in South Korea, told the charity: "One day the food distribution simply stopped. We didn't receive anything anymore.
"The government gave us the advice to go into the mountains, pluck grass and make soup with some salt. It tasted really awful, very bitter."
Open Doors' underground workers smuggle food to help keep 60,000 North Korean Christians alive each month, along with medicines, winter clothes, boots and blankets.
There are between 200,000 and 400,000 Christians in North Korea. However, it's difficult to get an exact figure, as Christians in North Korea must keep their faith completely secret.
Open Doors estimate between 50,000 and 70,000 Christians are imprisoned in labour camps - simply for their faith.
North Korea is ranked 1st on Open Door's World Watch List where believers receive the worst treatment.
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