More than 103,000 people have backed the Free Babar Ahmad campaign on the Government’s official e-petition website, making the issue eligible for a parliamentary debate in the House of Commons.
It is one of only five petitions which have reached 100,000 signatures.
Ahmad has spent seven years in British high-security prisons without trial as he fights extradition to the US on terror charges.
Calling on the Coalition to confirm a full parliamentary debate will now be held, his family said: “We are overwhelmed by the amount of support for Babar’s case.”
The American authorities accuse the computer expert of running websites that urged Muslims to fight holy war and conspiring to raise funds for al Qaida and the Taliban in Afghanistan.
But Ahmad strenuously denies the allegations and insists he is a peace-loving man dedicated to his family and his local community in Tooting.
Ahmad was first arrested by Metropolitan Police officers in a dawn raid on his home in December 2003 on suspicion of leading a group which provided al Qaida and other terror networks with computer, financial and logistical expertise.
British-born Ahmad was released six days after his arrest and has never been charged in the UK but was again held by Scotland Yard officers in August 2004 on an international arrest warrant issued by American federal authorities.
Ahmad, who has been imprisoned without charge for longer than any other British citizen detained since the 9/11 attacks, insists he is innocent and is fighting attempts to extradite him to the US to stand trial.