A study by British researchers has identified countries that would be worst affected in the event of a catastrophic asteroid strike on Earth.

Researchers at Southampton University say the list is largely made up of developed countries with large populations that would experience millions of deaths in such an event.

The United States, China, Indonesia, India and Japan are at risk on the basis of population while Canada, the United States, China, Japan and Sweden are rated most at risk in terms of potential damage to their infrastructure.

The list was compiled using software called NEOimpactor, using data from NASA's Near Earth Object program.

"The threat of Earth being hit by an asteroid is increasingly being accepted as the single greatest natural disaster hazard faced by humanity," Southampton's Nick Bailey, who developed the NEOimpactor software, told the Daily Telegraph.

"The consequences for human populations and infrastructure as a result of an impact are enormous."

He cited the devastation wreaked by an asteroid which landed in a remote area near the Tunguska River in Russia in 1908 as an indication of the impact such an event could have on a populated place.

"While it only flattened unpopulated forest, had it exploded over London it could have devastated everything within the M25," he said.

The M25 motorway is a "ring road" whose distance from central London varies between about 12 to 20 miles.