People for the Ethical Treatment of Animals (PETA) has sued SeaWorld for violating the rights of its killer whales under the 13 Amendment, which deals with the abolition of slavery.

PETA has filed a lawsuit against the Blackstone Group, a private equity firm, which recently acquired SeaWorld, for what it claims is the violation of the rights of five killer whales that are featured in its popular aquatic amusement park.

The lawsuit, which was filed Tuesday in a U.S. district court in San Diego Calif., lists as plaintiffs: Tilikum, Katina, Corky, Kasatka and Ulises -- five orcas at SeaWorld's parks in California and Florida.

PETA has enumerated the history of all five whales on its website and states, "It's time to end the slavery of orcas who are denied everything that is natural and important to them, exploited as breeding machines, and forced to perform for SeaWorld's profit. The public is ready, the orcas are definitely ready, and PETA believes that the law is on their side."

Ingrid Newkirk, president of PETA said: "All five of these orcas were violently seized from the ocean and taken from their families as babies." She added, "They are denied freedom and everything else that is natural and important to them while kept in small concrete tanks and reduced to performing stupid tricks."

An official at SeaWorld dismissed the suit and found it offensive that PETA would equate whales with human beings.

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This is not the first occasion in which PETA has suggested that animal rights were the same as human rights.

The controversial organization began a campaign in 2005 in which it presented several images of animal abuse juxtaposed with images of slavery and African-Americans.

The campaign incensed civil rights organizations, and prompted a statement from John White, a spokesman from the National Association for the Advancement of Colored People (NAACP), who, according to  The Associated Press, said: "PETA operates by getting publicity any way they can. They're comparing chickens to black people?"

Still PETA has never apologized for its stance on equating the issue of animal rights with that of human rights, this filed suit against the Blackstone Group is the latest effort in the activist group's continuing campaign.