It's enough to have Robert Redford quaking in his knee-length designer snow-boots. The latest victim of California's controversial decision to ban gay marriage could be the film star's pet project: the annual Sundance Film Festival.

January's star-studded extravaganza is held in Utah, home to the Mormon Church, which was instrumental in persuading 52.5 per cent of California's electorate to vote for Proposition 8, the ballot measure to outlaw same-sex weddings. Now gay rights campaigners are calling for Hollywood actors and directors to pull out of the movie festival as part of a wider consumer boycott of the state.

The Church of Jesus Christ of Latter-day Saints is headquartered in Salt Lake City and counts about 62 per cent of Utah residents as members. It provided thousands of activists and up to $40m (£27m) in funding to help Proposition 8 pass, leaving 18,000 recently-married gay couples in legal limbo.

After a week of noisy public protests, bloggers, gay rights activists and others seeking retribution against the Mormons are planning to disrupt the $6bn (£4bn)-a-year winter tourism industry, in which the week-long Sundance festival plays a central role.

"At a fundamental level, the Utah Mormons crossed the line on this one," said the blogger John Aravosis, who has organised boycotts against Microsoft and Ford over gay rights issues. "They just took marriage away from 20,000 couples and made their children bastards."

Mr Aravosis is calling for skiers to holiday in rival states such as Colorado, and for the sympathetic showbusiness community to turn its back on Sundance.

"The main focus is going to be going after the Utah brand," he said. "It is a hate state. It's high time Sundance found a better state to party in than the seat of the Mormon Church. Sundance is the gathering of liberal Hollywood. The last place it should be is in Utah."

Boycotting Sundance, which starts on 15 January 2009, would be tricky for many key movers and shakers in the film industry, as the festival plays a major role in promoting many of the big releases slated for next spring. It would require co-operation from scores of independent producers, who are already feeling the pinch from harsh market conditions.

Festival organisers say it is too late for a change of venue, and stress that Park City, where Sundance takes place, is one of the most liberal places in Utah. Instead, they hope activists will simply organise a boycott of local businesses that donated money to Proposition 8.

"Sundance was founded on the idea of championing diversity and freedom of expression," said a spokesman. "It would be a grave disappointment to us if our festival were to be singled out for a boycott."

Nonetheless, the proposed move has sparked concern among Utah's political class, many of whom object to their state's vilification. Scott McCoy, an openly gay state senator from Salt Lake City, said he hoped activists would refrain from tarring all locals with the same brush. "There are really good people here in Utah that are sympathetic to our cause," he said. "Rather than a boycott, I would have every gay person in the country come to Utah and show the people what genuine wonderful people and families we have."

Meanwhile, a judge cleared the way for gay marriage to begin yesterday in Connecticut. Couples immediately marched to New Haven City Hall to get marriage licences. Gay marriage is legal now only in Connecticut and Massachusetts.