ORLANDO, Fla. -- SeaWorld acknowledged that it sent its own workers to infiltrate an animal rights group which opposed the practices of the theme park.

The development comes months after People for the Ethical Treatment of Animals accused a SeaWorld employee of trying to incite violence while posing as a fellow animal rights activist.

SeaWorld Entertainment CEO Joel Manby vowed Thursday to end the practice, but said that it had sent its employees to protect the safety of its employees and customers.

"We recognize the need to ensure that all of our security and other activities align with our core values and ethical standards," Manby said.

However, the company refused to say who had authorized the infiltration, how long it had been going on, or how many workers were used to infiltrate animal rights groups or other opponents. SeaWorld spokeswoman Aimee Jeansonne Becka cited the confidential nature of its security practices.

The employee at the centre of the accusations by PETA, Paul McComb, is still employed by SeaWorld but working in another department, the company said Thursday.

PETA said last summer that its own investigation revealed that McComb, a human resource worker, attempted to incite protesters and had posted incendiary comments on social media while masquerading as an animal-rights activist since 2012.

PETA officials said Thursday that SeaWorld's refusal to fire McComb shows that it condones corporate spying. The group has been especially vocal in its criticism of SeaWorld since the 2013 documentary, "Blackfish," suggested the treatment of captive orcas provokes violent behaviour.

Park attendance dropped after the release of the documentary, which chronicled events at the park leading up to the death of a SeaWorld trainer in 2010.

"The tawdry orca sideshows and despicable spying tactics are sinking SeaWorld's ship," said Tracy Reiman, PETA's executive vice-president.

SeaWorld could face civil, and even criminal, legal exposure depending on the information it obtained from McComb about PETA and what the company did with the information, said Sharon Sandeen, a law professor at Mitchell Hamline School of Law in St. Paul, Minnesota.

If any information SeaWorld got from McComb met the definition of a trade secret -- it was secret, had value because it was secret and there was an effort by PETA to keep it secret -- then PETA could have a claim of trade secret misappropriation, she said.

"PETA would have to identify information that they said was misappropriated," Sandeen said. "They would have to show they had policies in place to keep the information secret."

SeaWorld Entertainment Inc. is hiring Freeh Group International Solutions to review oversight and controls over its security practices. The firm was founded by former FBI director, Louis Freeh.

Shares of the company plunged more than 11 per cent.