The four women closest to President Assad were added to the European Union's sanctions list at a meeting of Europe's foreign ministers today.
The Syrian leader's wife, mother, sister and sister-in-law will be added to the travel ban and asset freeze blacklist as the EU steps pressure on Assad's inner circle and family.
The inclusion of Asma al-Assad follows the leak of emails detailing her shopping sprees.
William Hague, the Foreign Secretary said: "Their behaviour continues to be murdering and totally unacceptable in the eyes of the world."
The 36-year-old former investment banker and the female relatives of regime members will join another eight government officials and two oil firms added to 114 Syrians and 38 organisations subject to freezes on their assets and bank accounts in EU member states.
EU and British officials have faith that the move will add to the "stranglehold" on the regime, though it has survived 11 previous rounds of sanctions.
Like others already listed, Mrs Assad is likely to be subject to an EU travel ban, though this would not prevent her travelling to Britain, if she has retained her British citizenship.
Born and raised in Acton, west London, she married Mr Assad in late 2000, the year he was installed as president following the death of his father, Hafez.
Her role in the president's inner circle has come under increased scrutiny after emails written by Syria's first couple were leaked by opposition activists.
They showed that as the government offensive that has claimed an estimated 7,000 lives intensified, she shopped online in London and Paris, spending tens of thousands of pounds on jewels, furniture and a Venetian glass vase from Harrods.
She used an alias to make purchases from Europe and asked a friend to acquire a copy of Harry Potter and the Deathly Hallows Part II for her two older children. In drawing up previous sanctions, the EU froze "all funds and economic resources" belonging to "persons responsible for the violent repression against the civilian population" or "persons and entities associated with them".
Mrs Assad may already have violated sanctions with her online shopping spree that could expose her to prosecution. The regulations prohibit EU citizens from making "funds or economic resources" available to anyone named on the list.
Before the protests against her husband's rule began a year ago, she cultivated the image of a glamorous yet serious-minded woman with strong Western-inspired values who would liberalise the ruling family and the country. A glowing article in Vogue magazine described her as "a rose in the desert" and her household as "wildly democratic".
That image crumbled when her husband responded to the anti-government rebellion with extreme violence. She has shown no sign of the inner torment that some who met her beforehand assumed she was going through. Her messages to her husband and her friends are utterly supportive of him and at times display a resolve to see the crisis out.
"If we are strong together, we will overcome this togethere_SLps I love you," she wrote to her husband on Dec 28.
In her only statement since the crisis broke out, she said: "The president is the president of Syria, not a faction of Syrians, and the first lady supports him in that role." The emails also show that her father, Fawaz Akhras, a cardiologist at London's Cromwell hospital who has a private practice on Harley Street, regularly provided advice to Mr Assad on media and public relations policy.
"She and her father are accomplices to this crime. They learned nothing from the democracy here in the UK," said an opponent of the regime in London who asked to be named as Fawaz. He claimed that Mrs Assad had become a hate figure for many in the expatriate community of which she was once a part.
"They have stolen Syrian money. She is squandering it here in London," he said.
