Dr Abbas Khan's sister, Sara, has told ITV News that she expects the British government to get answers from the Syrian regime. "This is the least they can do," she added.
David Cameron has written to the mother of a British doctor who died in custody in Syria, describing his death as "a sickening tragedy".
The mother of British doctor Abbas Khan, who died after 13 months in a Syrian prison, has accused the regime of "murdering" her son.
Relatives of British surgeon Dr Abbas Khan have said they do not understand what led to his death just days before he was due to be released