Miranda Kerr will get flexi in free yoga class

Miranda Kerr will conduct a free yoga class for 500 fans who upload their own I Will If You Will challenge. Photo / AP, Rob Griffith

Miranda Kerr has pledged to conduct a free yoga class for 500 fans as part of a new Earth Hour campaign.

Kerr has been announced as an Earth Hour global ambassador for the second consecutive year to use her voice to inspire people to participate in the I Will If You Will campaign.

The campaign aims to encourages folks to go beyond the traditional hour, where people are asked to switch off their lights and take more positive action for the environment by setting a personal challenge.

The first 500 people to upload their own I Will If You Will challenge, on www.youtube.com/earthhour, will be awarded with a free yoga class conducted by Kerr.

"I hope my first challenge inspires my friends, family and fans to make their own promise for the environment," Kerr says.

The globe-trotting model from rural NSW has also committed to reducing her carbon footprint by offsetting all of her travel.

"If we all adopt simple practices like recycling, switching to energy-efficient lighting or paperless banking then we can make a difference together," Kerr says.

The first-ever Earth Hour started in Sydney in 2006 and has now grown to a 5251-city-strong global movement, last year reaching 1.8 billion people in 135 countries across all seven continents.

This year's Earth Hour takes place between 8.30pm and 9.30pm on Saturday, March 31.

- AAP