The father of British photojournalist John Cantlie has urged his Islamic State jihadist captors to release him to those “he loves and who love him”, saying he was only in Syria to help.

Speaking on Friday from a hospital bed with the aid of an electrolarynx, Paul Cantlie revealed his joy at seeing a video of his son, who went missing in Syria in November 2012, but also the ongoing pain felt over his detention.

“For the first time in almost two years, we saw John when he made a televised broadcast during which he told viewers that he was still a prisoner of the Islamic State and that maybe he will live and maybe he will die,” the 81-year-old explained.

“As a family we experienced great relief seeing and hearing John and knowing that he is alive. This was followed by the feeling of despair and helplessness.”

Some thought Cantlie was dead but the 43-year-old resurfaced last month in a video, dressed in an orange jumpsuit in an unidentified location.

Cantlie said he was being held as a prisoner and promised to reveal in a series of programs the “truth” about the jihadist group that has seized parts of Iraq and Syria.

He has since appeared in two further videos, and in the most recent, released earlier this week, delivered a scripted message criticising the US strategy for dealing with IS.

Father Paul said his son, who was kidnapped along with executed US journalist James Foley, was only “seeking out the true story of the suffering of the Syrian people”.

“As an impartial and respected journalist he knew that he could make a difference by acting as a platform for the world to listen to and take notice, using his journalistic skills for the good of the people, as a friend and as a civilian,” he said.

“To those holding John: please know that he is a good man, he sought only to help the Syrian people and I ask you from all that is sacred, to help us and allow him to return home safely to those he loves and who love him.”

He also revealed that the family had been trying to deliver “an important message regarding John” to IS militants, but had received no response.