The union-led boycott against 14 large San Francisco hotels has sapped another 1,500 room nights from the city, with an additional potential cancellation threatening hundreds more.

Groups relocating their events now include the California Applicant Attorneys Association, which will move its 800-person annual conference from San Francisco, where it was booked for a six-day event at the Hyatt Regency, to an undetermined location. The association, which represents worker's compensation lawyers, said the move was prompted by the union boycott.

"We cannot go to any place that has a dispute," said Executive Director Karen Locke, citing the group's bylaws.

The impact on San Francisco will be significant. The event was to consume 450 rooms on its peak night, close to half the capacity of the 805-room Hyatt Regency. All told, it consumes close to 1,500 room nights

Locke added that moving the event to Moscone West is not a realistic option due to the cost. Also, the group is uncertain whether there is enough room in hotels not targeted by the boycott.

The attorneys group is exploring other locations, mostly in the Los Angeles area.

Another group says it is thinking about moving its event. The Independent Television Service said in a statement on its web site it is in an "untenable situation" with its planned May 1-6 International Public Television Conference at Hilton San Francisco, expected to draw close to 2,000 people and consume 800 hotel rooms on its busiest night.

"We've spent 15 years committed to television that values economic and social justice," CEO Sally Jo Fifer wrote in the statement. "Now, we find ourselves in a position where we support employee health benefits; and yet, we must host this important conference."

Fifer also said the group stands to forfeit at least $663,000 if it backs out of the Hilton contract. Close to half of that money was raised from outside sources.

Fifer said the group is exploring its options with both Hilton and the hotel workers' union, Local 2 of Unite Here. A spokesman for the group said earlier this week that the web statement represents the group's most current thinking.

Hotel industry sources say the losses are painful for properties throughout the city because, after a cancellation, an individual hotel will typically have to use steep discounting to fill a large and suddenly vacant block of rooms. This, in turn, puts pressure on other hotels to cut prices.

No talks are scheduled between the hotel union and the hotels at this time.

Parties outside the talks are urging the two sides to meet, with some asking Mayor Gavin Newsom to play a larger role in bringing the two sides together. The San Francisco Chamber of Commerce, Union Square Association and other business groups have convened meetings to discuss the situation.

"We'd like to see him just put a little more pressure to lock the people in a room," said Ryan Chamberlain, field director to advocacy group SFSOS and a party to the talks. "It's pretty much all he can do at this point."

Linda Mjellem, executive director of the Union Square Association, said the continuing cancellations will hurt the city for years to come.

"The conventions we lose today are the tip of the iceberg," Mjellem said. "It's not just the conventions we know about, it's the ones that book far ahead who probably aren't making those booking decisions.

"It has a ripple effect on businesses throughout the city."

Ryan Tate covers hospitality for the San Francisco Business Times.