From left, Big Love cast members Ginnifer Goodwin, Jeanne Tripplehorn, Bill Paxton and Chloe Sevigny pose at the show's third season premiere in Los Angeles on Jan. 14. (Chris Pizzello/Associated Press)

The producers of the polygamy TV drama Big Love have apologized ahead of time for any offence to Mormons caused by an episode that depicts a sacred religious rite.

The HBO cable series stars Bill Paxton as the owner of a chain of hardware stores who is married to three wives, played by Jeanne Tripplehorn, Chloe Sevigny and Ginnifer Goodwin.

The fictional family is non-Mormon but the series will show an endowment ceremony in a Mormon temple on its March 15 show.

The Mormon Church, officially known as the Church of Jesus Christ of Latter-day Saints (LDS), only allows selected individuals and members in good standing to witness such a ceremony.

News of the episode has angered many Mormons, who have called for a boycott of the network and calls to cancel subscriptions to AOL, part of the Time Warner Inc. conglomerate that owns HBO.

The network released a statement late Tuesday to address the outrage.

"It was not our intention to do anything disrespectful to the church, but to those who may be offended we offer our sincere apology."

Used ex-Mormon as consultant on show

Creators Mark V. Olsen and Will Scheffer told TV Guide the episode will take place in an endowment room and the celestial room of a Mormon temple. They said they thoroughly researched the ritual and used an "ex-Mormon consultant."

The two say the ceremony — in which participants move to a higher level of understanding of their religion — has never been depicted on screen.

The Mormon Church has previously voiced fears about the series, which launched in 2006. In a release, it says it feels a betrayed by HBO.

"Despite earlier assurances from HBO, it once again blurs the distinctions between the Church of Jesus Christ of Latter-day Saints and the show's fictional non-Mormon characters and their practices. Such things say much more about the insensitivities of writers, producers and TV executives than they say about Latter-day Saints."

The church did not call for a boycott but did say that individual members could do what they wanted.

The church says more Mormon themes are being knitted into the show's plots and Mormons tend to be portrayed as self-righteous and unsympathetic.

The Mormon Church, based in Utah, has some 13.5 million members around the world.

Founded in 1830, it officially banned polygamy in 1890. But polygamy is still practised by some breakaway sects.