America must suspend the $1.3 billion (£830 million) it gives Egypt in military aid in the wake of yesterday's violence, Labour has demanded.
The demand is a sign Labour is preparing to adopt a more hardline position on Egypt following the killing of hundreds of people yesterday.
"It was right for the United States to try, through quiet diplomacy, to influence the Egyptian military authorities towards a democratic path after their removal of President Morsi," shadow foreign secretary Douglas Alexander said.
"Yet recent days have seen horrific bloodshed. The time has now come for the UK government to urge the US administration to suspend its $1.3bn military aid to Egypt.
"This suspension should be maintained while the US government's review into its relationship with the Egyptian state continues."
Alexander also called for an immediate meeting of EU foreign ministers to "review all existing support and aid provided directly to the Egyptian authorities".
He added: "The UK government should therefore urge the interim government to suspend the state of emergency currently in place and commit to a fixed timetable for holding new elections."
The UK and US governments have been criticised for not taking a tough enough line with the Egyptian army since it replaced Morsi in a popularly-backed coup in July.
Some say the moderately critical statements – complete with careful use of the phrase "on both sides" – are evidence of tacit consent for the army's behaviour.
Foreign secretary William Hague said: "I am deeply concerned at the escalating violence and unrest in Egypt, and regret the loss of life on all sides.
"I condemn the use of force in clearing protests and call on the security forces to act with restraint.
"Leaders on all sides must work to reduce the risk of further violence."
The government says 525 people died nationwide yesterday after the army moved in to close down two protest camps, but the Muslim Brotherhood puts the figure closer to the 2,000 mark.
This afternoon, hundreds of Muslim Brotherhood supporters stormed a government building in Cairo and set it on fire, according to Egyptian state media.
The party has called for marches in Cairo and Egypt's second city, Alexandria, to protest against the killings.