Amnesty UK carried out the protest against what it calls “Britain's shameful response to the refugee and migrant crisis”.
The body bag protest was staged on the eve of an emergency meeting of European leaders in Brussels to discuss the matter.
More than 1,000 men, women and children have died trying to enter Europe in overcrowded boats crossing the Mediterranean and Aegean Seas in the last six days.
“The equivalent of five passenger planes full of people have drowned last week alone, and this is only the start of the summer. If they had been holiday makers, instead of migrants, imagine the response,” said Amnesty UK director Kate Allen.
According to the United Nations High Commission for Refugees, April has had the highest number of casualties ever recorded in the Mediterranean – and that number is expected to rise when we reach the warmer summer months, where more people attempt the crossing.
Even before last weekend's tragic incident, in which around 800 people are believed to have died, Amnesty says the number of fatalities was up 50-times on 2014 as refugees seek to leave Syria via Libya.
Party leaders including Ed Miliband, David Cameron and Nick Clegg have all said more must be done to prevent these deaths but Amnesty is calling for people to put pressure on them to act immediately.
“It’s essential they agree to strengthen search and rescue operations in the Mediterranean and the Aegean seas through a joint effort involving all EU countries,” the pressure group said. “With political will, this could be done within days.”