The US Secretary of State John Kerry said the continued violence in Syria showed that it was time for President Bashar al-Assad to go.
Speaking alongside Kerry, Foreign Secretary William Hague called for support for Syria's opposition to be increased significantly to bring the conflict to an end.
More top news
Singer Adele and Hollywood star Jennifer Lawrence were among the protesters on the anniversary of the US president's inauguration.
The proposals are being introduced in order to help create more equality in the treatment of physical and mental health.
The prime minister said "tough new rules" will be introduced to tackle the behaviour of executives who put their workers' pensions at risk.