The comic - who was raised Catholic - has frequently criticised the Catholic Church for the worldwide sex abuse scandal, in addition to mocking organised religion in his film Religulous.
Watch the Religulous trailer below:
Bill Donohue of the Catholic League has now written an open letter to HBO's parent company to demand that Maher no longer be allowed to lampoon religion on his show.
Donohue wrote: "There is no other entertainer in the nation who has repeatedly spoken about the Catholic Church, especially its priests, in more vile and obscene terms than Bill Maher.
"Vicious beyond belief, his remarks would be condemned - indeed he would be fired - if directed at any other demographic group. Over and over again he libels priests, portraying all of them as sexual abusers. And he does so with impunity."
Donohue went on to claim that Maher has made 39 jokes at the expense of Catholics over the years, adding that such a large-scale attack on one religion is unacceptable.
"Catholics need to know just how far Time Warner is prepared to play the role of spectator," Donohue wrote.
"Does stewardship not count at all? HBO has been contacted many times, but nothing changes... The time has come for someone in a position of responsibility to sit down and have a serious talk with this man."
Donohue has been a vocal critic of a perceived anti-Catholic bias in the entertainment industry, previously aiming protests at Larry David, Lady GaGa, Jamie Foxx and model Lucy Pinder.