The wife of British hostage Alan Henning has urged Islamic State to release him after she received an audio message from her husband pleading for his life.

Barbara Henning called for the militant group to "open their hears and minds" and said she had been told that a Sharia court had found her husband innocent of being a spy.

In a statement issued by the Foreign Office, she said: "I have a further message for Islamic State.

"An audio file of Alan pleading for his life has just been received by me.

"I and people representing me continue to reach out to those holding Alan.

"Islamic State continue to ignore our pleas to open dialogue.

"I have seen Muslims across the globe question Islamic State over Alan's fate. The voices of the people have spoken out loud and clear. He was working with Muslims to help the most vulnerable within Syria. Nothing has changed. He went to Syria to help his Muslim friends deliver much needed aid.

"We are at a loss why those leading Islamic State cannot open their hearts and minds to the facts surrounding Alan's imprisonment and why they continue to threaten his life.

"I have been told that he has been to a Sharia court and found innocent of being a spy and declared to be no threat. I implore Islamic State to abide by the decisions of their own justice system.

"Please release Alan."

Mr Henning, 47, was part of an aid convoy taking medical supplies to a hospital in northwest Syria in December last year when it was stopped by gunmen and he was abducted.

Earlier this month, David Haines, 44, who was raised in Perth, was murdered by the Islamic State.

In it, a masked man who killed Mr Haines said Henning would also be killed if Prime Minister David Cameron kept supporting the fight against the militants.