A 15-year-old has been arrested in the latest bias attack on Staten Island, accused of beating a Mexican-American teen who volunteers with an anti-bias group.

“One bias crime is one bias crime too many, and we’ll do everything we can to stop it,” Mayor Bloomberg said yesterday after the 11th reported bias attack in Port Richmond since April.

“This is just an outrage.”

The victim, Cristian Vazquez, 18, was attacked early Saturday as he was returning from Manhattan.

He will be a senior at Susan Wagner HS and volunteers with Eye Openers: Youth Against Violence, said the Rev. Terry Troia, a community activist.

The suspect, a Liberian native who holds US citizenship, faces hate-crime charges of assault, robbery and aggravated harassment. Two more assailants are being sought, police said.