NEW YORK -- The Muppets Studio is blaming "unacceptable business conduct" for its dismissal of Steve Whitmire as the longtime performer of Kermit the Frog.

This explanation, issued Monday, follows Whitmire's emotional blog post last week after his firing was made public. He said he learned last October that the role of Kermit would be recast.

Whitmire had been with the Muppets since 1978, and took over as Kermit after the untimely death of Muppets founder Jim Henson in 1990. Whitmire was reportedly chosen by Henson's son, Brian, CBS New York reported.

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The two made TV appearances on "Late Night with Jimmy Fallon," ''30 Rock" and "Saturday Night Live" and in films like "Muppets Most Wanted" and "The Muppets."

The Muppets Studio did not detail the nature of Whitmire's "repeated unacceptable business conduct," but said it spanned "a period of many years," adding that "he consistently failed to address" his employers' feedback.

Whitmire could not immediately be reached for comment, but in an interview Monday with The Hollywood Reporter he said the studio felt he had been too outspoken in expressing how the Kermit character should be portrayed on the ABC prime-time Muppets mockumentary series that aired in 2015-16. Whitmire said he had only been trying to help keep the show "on track."

The studio said veteran Muppets performer Matt Vogel is now taking over as Kermit.

Henson's daughter and son told The New York Times Monday that they supported the decision to fire Whitmire.

Henson's daughter, Lisa, told the Times that Whitmire refused to train an understudy for low-level performances and "played brinkmanship very aggressively in contract negotiations." Lisa Henson is president of the Jim Henson Co., which sold The Muppets brand to Disney in 2004.

Brian Henson, who is the company's chairman, told the Times that Whitmore often sent emails attacking writers, directors and others involved in Muppets projects.