Aljazeera on Wednesday aired a video showing Hassan, who was seized by unknown captors in Baghdad last week, standing in a dimly lit room.
"Please release the women prisoners from the prison in Iraq," said a tired looking Hassan, director of the Care International charity in Iraq.
"She appealed to ... British Prime Minister Tony Blair to withdraw troops from Iraq and not deploy them in Baghdad. She asked the British government to release Iraqi women from prisons," Aljazeera reported, quoting the video.
Aljazeera said Hassan also asked Care International employees to end their operations in Iraq. The charity suspended its work in the country after Hassan was seized.
In London, the British foreign office on Wednesday said: "We will consider very carefully what response, if any, to make to this latest video."
'Miss my wife'
Earlier, Tahsin Ali Hassan, the Iraqi husband of Margaret Hassan, called on the captors to release her.
Margaret's husband Tahsin has
appealed for her release
"Margaret has always worked to serve the Iraqi people," he said. "She has made a lot of contribution in the field of relief and human services.
"A week has passed since Margaret was taken from me. I miss my wife and so do her family, friends and colleagues," he said.
Addressing the captors, Hassan said "I have asked you to release her before. But now, and in the name of Islam, I call upon you to bring Margaret back to me safely."
Hassan, who holds British, Irish and Iraqi citizenship and has lived in Iraq for the past 30 years, was seized on her way to work in Baghdad on 19 October.
No group has claimed responsibility for her abduction.