The Foreign Secretary is being urged to act as China continues its policy of repatriating North Korean escapees.
The appeal comes from Timothy Cho, an escapee from North Korea who now lives in the UK and works for Christian anti-persecution charity Open Doors.
He makes the call in a letter signed jointly by Lord Alton of Liverpool, and Benedict Rogers, Deputy Chair of the Conservative Party Human Rights Commission.
The letter has been sent to Dominic Raab following the forced repatriation of 50 North Korean escapees by Chinese authorities earlier this month.
Together, they plead with Raab to persuade China to deport the escapees to South Korea instead, where they will be allowed to remain under its 'one Korea' policy.
"These North Koreans will without doubt end up in prison and labour camps where they will very likely die, either by execution or as a result of the dire conditions and mistreatment," they tell Mr Raab in the letter.
"North Korean escapees have already endured enormous grief, pain and trauma ... The news of their forced repatriation creates significant fear, as they await their fate of interrogation, imprisonment, torture and even death in North Korea."
Cho said there were probably hundreds more North Korean men and women in Chinese prisons waiting to learn their fate.
"This policy of repatriation has been going on for decades now," he said.
"China has forcibly repatriated hundreds of thousands of escapees from the nation, which it borders.
"China keeps bowing to pressure from North Korea's leadership. This must not be the fate of North Korean escapees who simply ask to continue their journey via China to South Korea, who will automatically receive its 'one Korea' policy.
"Let us stand with North Korean escapees who need the assistance and protection they so desperately need."
Open Doors warns that those trying to escape North Korea include many Christian converts who risk being sent to harsh gulags if their faith is discovered.
The open letter coincides with the launch of a new All Party Parliamentary Group Inquiry report into human rights abuses in North Korea, which says that officials in the hermit communist country are guilty of murder, torture, modern-day slavery, infanticide, forced abortions and religious persecution.
"[T]here are reasons to believe that some of the atrocities reach the threshold of genocide, particularly in relation to three groups: Christians; half-Chinese children; and the 'hostile' group," the report reads.