Leonardo DiCaprio and Oprah Winfrey are the greenest celebrities in the world, according to a new poll to unearth the most popular eco-friendly stars.

DiCaprio beat off competition from Bono, Brad Pitt and actor Ed Begley Jr. to top the male category in the survey, which was carried out by GreenDaily.com and Bebo.com, to mark Earth Day on Wednesday.

Winfrey out-shined Angelina Jolie, Hayden Panettiere, Gwyneth Paltrow and Sir Paul McCartney's ex-wife Heather Mills to lead the female category.

Singer Mariah Carey was ruled to be the least environmentally friendly star, following reports she regularly flies her personal trainer from the Caribbean to New York to keep her fit.

Jet-setting superstar John Travolta joined her on the hit list, after research found the qualified pilot generates 800 tons of carbon emissions each year flying around the world.