Miley Cyrus and Kelly Osbourne in fundraising race

Miley Cyrus is going head-to-head with her pal Kelly Osbourne to see who can raise the most money for an animal charity.

The stars, who became friends while filming upcoming comedy So Undercover together, have each asked their fans to help them pull in the highest amount in the Twitter for the Critters challenge.

Osbourne has been busy begging followers to put her in first place so she can make the biggest contribution to The Onyx And Breezy Foundation.

In posts on her Twitter.com page, she writes, "Help me save puppies by donating for me... every dollar goes to the animals. I love animals, help me save lives by voting for me. Thank you for the support!"

The duo faces stiff competition from Cyrus' country singer dad Billy Ray, Twilight actor Peter Facinelli and Modern Family star Eric Stonestreet, who are heading up the remaining three celebrity teams in the fundraising contest.

A poster signed by 89 A-listers including Dame Helen Mirren, Clint Eastwood, Drew Barrymore, Charlize Theron, Matt Damon and Alec Baldwin will be presented to one lucky fan from the winning team.

The Onyx And Breezy Foundation is a non-profit charity devoted to lending financial support to organisations benefiting animal welfare.