Foreign Secretary William Hague today welcomed "another tightening of the screw" against the regime of Syria's president Bashar al-Assad as his wife was banned from travelling to the EU.
However there was confusion about whether British-born Asma-al-Assad, 36, could legally be banned from the UK after Europe's foreign ministers added her to a EU list of undesirables.
The president's wife joins a register of more than 100 members of the ruling regime - which already includes her husband - whose European travel visas are blocked and whose European-held financial assets are frozen.
Because the president's wife was born in the EU, it is unclear whether she can legally be denied access to her own country of origin.
However Mr Hague said she was unlikely to try to enter the UK. "Given what we have done... we are not expecting Mrs Assad to try to travel to the UK at the moment," he said.
The decision to add Mrs Assad and about a dozen others to the existing list of those facing sanctions, was nodded through at talks in Brussels in the wake of continuing government repression of popular opposition in Syria.
Mr Hague said: "It is very important to increase the pressure on the Syrian regime. Their behaviour continues to be murdering and totally unacceptable in the eyes of the world."
He welcomed new UN calls for humanitarian access to war-torn areas and an end to government-backed violence against opponents of the Assad regime.
"The UN Security Council has spoken in a united way and it is important that the EU adds to that pressure on the regime with sanctions. It is important that we tighten the diplomatic, economic and diplomatic stranglehold on them," he added.
As well as the travel visa and asset bans on individuals associated with the regime, EU sanctions against Syria already include an arms embargo, and a ban on EU exports of oil and gas equipment to Syria.
The latest round of measures came in late February when the EU tightened the economic noose against president Assad's government, freezing the assets of the Central Bank of Syria and restricting the Syrian regime's access to the gold and precious metals market.
The measures - the thirteenth round of EU sanctions against Syria - added Mrs Assad and a dozen others close to the regime in power to the sanctions list.
Adding the president's wife reflects fury at Mrs Assad's declaration in a letter to the Times earlier this year that her husband remained the right man to run Syria.
Since then the previously low-profile presidential wife, originally from west London, has been spotlighted as continuing to enjoy the high life despite the continuing assault on entire communities in Syria which has resulted in thousands of deaths.
EU foreign policy chief Catherine Ashton said: "I do think sanctions are putting pressure on the regime.
"Sanctions target entities in a way that prevents them from carrying on business as usual and they make a strong political statement about how the international community feels about what is going on."
She added: "Sanctions are a very important tool but they are not everything and they are always within a political framework of trying to move things forward.
"That's what we've seen with the statement at the UN in the last couple of days and many different efforts are going on in a coordinated way."
Before returning to London, Mr Hague said: "British nationals, British passport holders, do obviously have a right of entry to the United Kingdom, but given that we are imposing an asset freeze on all of these individuals and a travel ban on other members of the same family and the regime, we are not expecting Mrs Assad to try to travel to the United Kingdom at the moment."
In a statement the Foreign Secretary said he welcomed the extension of existing sanctions to an additional two oil companies and "a further 12 individuals closely associated with the brutal repression being carried out by the Syrian regime".
He continued: "This is a further step in tightening the economic and diplomatic stranglehold on this criminal regime.
"The message to those who continue to side with Assad is clear - the violence must end and those responsible will be held to account."