Both locations saw violence, looting, arson and aggression against the police, following the shooting of Tottenham man Mark Dugan. Riots quickly spread across the country for several evenings last August.
These events are seen as the main cause for the slip for London and Manchester in The Economist Intelligence Unit survey, the former dropping two places to number 55, and the latter falling by nine to 51.
The editor of the annual survey was Jon Copestake, and he said that the UK cities had seen “a slight downgrade in liveability due to the mass outbreaks of civil unrest that took place last year", and their standings suffered as a result.
He added that the Olympics had been a "definite boost for London's profile", but failed to change their standing in the survey because, "London was already among the world's most vibrant cities, with plenty to see and do, so [the Olympics] has had no impact on overall lifestyle.”
Melbourne in Australia has been named as the world’s most liveable city, with Bangladeshi capital Dhaka coming in last place.