Home Secretary Charles Clarke has authorised Babar Ahmad's extradition to face terrorism charges in the US.
Mr Ahmad is set to appeal against the extradition order
The decision follows a long fight by the US for his removal and by Mr Ahmad and his supporters against the move.
The 31-year-old computer expert from Tooting, south London, is accused of running websites supporting terrorism and urging Muslims to fight a holy war.
He was arrested under anti-terror laws in August 2004 and charged with terror crimes by a US court two months later.
He was previously arrested under anti-terror laws in December 2003, but was released without charge - a move his supporters say proves his innocence.
His lawyers say Mr Ahmad denies the charges and his father Ashfaq Ahmad, has said his son is "totally innocent" and the case against him "ridiculous".
His lawyers also say Mr Ahmad, who is being held in Woodhill Prison, Milton Keynes, would be at risk of the death penalty if he was sent to the US.
Last autumn a Connecticut court charged Mr Ahmad, a British citizen, with supporting terrorism, conspiring to kill Americans and of money laundering.
The charges were brought in the US as Mr Ahmad allegedly used US-based websites to recruit fighters for causes in Afghanistan and Chechnya.
In claims dating back to 1997, the US government accused Mr Ahmad of "conspiring to support terrorism", saying he "sought, invited and solicited contributions" via websites and e-mails.
The US Department of State has claimed he ran several websites urging Muslims to use "every means at their disposal" to train for jihad, or holy war.
It is also alleged Mr Ahmad tried to set up a terrorist training camp in Arizona.
The websites allegedly encouraged people to train in street combat, land mine operations and sniper combat.
"If you're supporting the Taleban and the Taleban is killing American soldiers, we're alleging you're conspiring to kill American citizens abroad," Connecticut US Attorney Kevin O'Connor said in October 2004.
Mr Ahmad also had classified military documents describing the movements and formations of a Navy battle group and was in e-mail contact with an enlisted man aboard the USS Benfold, a Navy destroyer, US authorities said.
He was also charged with maintaining e-mail contact with a Chechen rebel leader.
John Hardy appeared for the US State department at Mr Ahmad's extradition hearing in March.
He told the hearing that one site, called azzam.com, which operated via US service providers from 1997 to 2003, included a posting reading: "Military training is an Islamic obligation, not an option."
It also carried a declaration of war against US forces in the Arabian peninsular from Osama bin Laden, Mr Hardy said.
He said another site carried an appeal for "tens of thousands" of gas masks and nuclear, chemical and biological warfare suits.
In May 2005, a District Court judge ruled Mr Ahmed could be extradited and the case was sent to the home secretary for final approval.
The order comes under UK legislation designed to speed up the extradition of suspected terrorists, which came into force in January 2004.
Babar Ahmad's father says the case against his son is "ridiculous".
Under the act there is no requirement for US authorities to represent a prima facie case - although UK authorities must do so in seeking extraditions from the US.
Mr Ahmad, his family and supporters, have waged a long fight against his extradition, which has included letters and public campaigns.
His family have already said they would appeal against the extradition order in the High Court.
In August 2004 his father, a retired civil servant, said his son was "an average, law-abiding young man who has never been in trouble".
Mr Ahmad, 69, also told the BBC News website: "I am no match for the resources of the United States, but I will do everything in my power to help my son."
He added: "My son is not a terrorist - he is junior IT support officer."
His campaign has also won support from Martin Mubanga, a British man held in Guantanamo Bay for nearly three years.
He joined protesters outside court at the hearing in March. Mr Mubanga, 32, said Mr Ahmad would not get a fair trial in the US and called for the extradition requests to be denied.