Foreign Office minister Hugh Robertson has accused the Syrian government of "in effect" murdering British surgeon Dr Abbas Khan.
The brother of a British surgeon, who died in Syria, has said his family has felt "abandoned by the officials in our country and abroad".
Shahnawaz Khan told ITV News that British authorities treated his brother "like he's been caught drinking on the streets of Dubai" instead of as a humanitarian aid worker.
The Foreign Office insisted they will pressing the Syrian regime for answers over Dr Abbas Khan's "tragic" death in prison following a year in custody.
"If these tragic reports are true responsibility for Dr Khan’s death lies with them and we will be pressing for answers about what happened," the FCO statement read.
“We have consistently sought consular access to Dr Khan and information on his detention, directly and through the Russians, Czechs and others.
"In November Minister Robertson wrote making clear our concerns about his welfare and treatment, stressing that the regime’s failure to provide any information that would indicate Dr Khan’s continued detention is legitimate meant his position should be reviewed immediately.
"These requests have consistently been ignored.
“All UK consular services in Syria were suspended some time ago and we continue to advise against all travel to Syria.”
George Galloway, who had been negotiating with the Syrian authorities to secure Dr Abbas Khan's freedom, has revealed he was due to fly to Damascus on Friday to bring the British surgeon back to Britain.
"I think we will have to wait for clarification on how exactly he died, but this is heartbreaking and devastating news for his family who have been working so hard for so long to secure his release.
"Particularly because his freedom had been agreed and he was due to return with me in the next few days."
The MP for Bradford West said he had been in contact with representatives of the Syrian government including the president and the foreign minister many times.
"Last week I received a call from the foreign minister telling me that the president had asked him to contact me to come to Damascus to bring Dr Khan home before Christmas.
"Obviously this had to be kept confidential but the family were kept fully informed. I was in the process of booking a flight for this Friday when I got the appalling news."
Dr Abbas Khan, who died after being imprisoned by Syrian security forces as he helped casualties of war, was due to be released from prison this week, his brother has claimed.
Afroze Khan told the BBC: "My brother was going to be released at the end of the week. We were given assurance by the Syrian government.
"My brother knew that. He was ready to come back home. He was happy and looking forward to being released."
The 34-year-old said the family was angry at the Foreign Office for "dragging their feet" for more than a year.
The family of a British doctor who died in a Syrian prison have claimed that he did not die in his cell, telling ITV News he was taken by "intelligence sources".
Dr Abbas Khan's sister confirmed the surgeon had died after being held as a prisoner in Syria for over a year.
Abbas Family anxious to stress their brother did not die in prison as is being reported. But was taken from prison by "intelligence sources"
Mother last saw her son Dr Abbas in Damascus 10 days ago. The family were preparing for his homecoming before Christmas
The family have said they are not satisfied with the official account of the death given to them by the Syrian national security services, and want a proper post mortem examination and further answers.
The Foreign Office said they are "extremely concerned" over reports that British surgeon Dr Abbas Khan has died in a Syrian prison.
A statement read:
We are extremely concerned by reports that a British national has died in detention in Syria.
We are urgently seeking clarification of this from the Syrian authorities.
The sister of a British surgeon who died in a Syrian prison after being held for more than a year has described him as the "finest brother a family could have".
Dr Abbas Khan's sister told ITV News' Social Affairs Editor Penny Marshall that her fine and courageous family is in mourning.
She said the family are determined to repatriate Dr Khan's body.