Microsoft's claim that its Edge browser is the thriftiest with power has drawn a sharp response from rival browser biz Opera, who called for open testing to work out which app provides better battery life.

Earlier this week, Microsoft released research which, it claims, shows that the Edge browser that comes with Windows 10 uses less power than its rivals – although it didn't include its own legacy Internet Explorer browser in that test. But Opera claims its openly replicable tests tell a different story.