LISBON, Portugal — The agency that sets the Internet addressing guidelines influencing how people navigate the Web defeated a proposal Friday to give adult Web sites their own “.xxx” domain.

Many in the adult-entertainment industry and religious groups alike had criticized the plan, which the Canadian government also warned this week could leave the Internet Corporation for Assigned Names and Numbers in the tricky business of content regulation.

The 9-5 decision by ICANN’s board came nearly seven years after the proposal was first floated by ICM Registry LLC. It was the third time ICANN has rejected such a bid. Paul Twomey, ICANN’s chief executive, who had described the proposal this week as “clearly controversial, clearly polarizing” abstained from the vote but did not say why.

“We are extremely disappointed by the board’s action today,” said Stuart Lawley, ICM’s president and chief executive. “It is not supportable for any of the reasons articulated by the board, ignores the rules ICANN itself adopted for the RFP (request for proposal), and makes a mockery of ICANN bylaws’ prohibition of unjustifiable discriminatory treatment.”

He added that ICM would pursue the matter further and when pressed by an Associated Press reporter if that could include a lawsuit against ICANN, Lawley said: “I would go so far as to say likely.”

What is certain is that ICANN will no longer hear the proposal but that does not mean that an entirely new application could be drawn up and offered for consideration.

Nearly all of the board members who voted against approving the domain said they were concerned about the possibility that ICANN could find itself in the content regulation business if the domain name was approved. Others criticized that, saying ICANN should not block new domains over fears like that, noting that local, state and national laws could be used to decide what is pornographic and what is not.

“My decision turned on one point and one point only,” said board member Steve Goldstein ahead of the vote. “The last point in our board’s resolution that under the revised agreement that we, ICANN, would be forced to assume ongoing management and oversight roles regarding the content and that is inconsistent with ICANN’s technical mandate.”

Lawley criticized ICANN board members who said they feared the domain would result in content management, telling the AP that “the part of the contract they are now claiming would lead them to content management was put in by them during the contract negotiations.”

Other board members said they believed that opposition to the domain by the adult industry, including Web masters, content providers and others, was proof that the issue was divisive and that “.xxx” was not a welcome domain.

“This application doesn’t meet the request for proposals mainly on the supporting community,” said board member Raimundo Beca of Chile, who voted against the domain. The adult industry, he added, “has been from the very beginning so split about this.”

Porn sites opposed to “.xxx” were largely concerned that the domain name, while billed as voluntary, would make it easier for governments to later mandate its use and “essentially ghettoize sexual information on the Web,” Kernes said.

ICM though had said it would fight any government effort to compel its use and cited preregistrations of more than 76,000 names as evidence of support.

Religious groups worried that “.xxx” would legitimize and expand the number of adults sites, which more than a third of U.S. Internet users visit each month, according to comScore Media Metrix. The Web site measurement firm said 4 percent of all Web traffic and 2 percent of all time spent Web surfing involved an adult site.

It was the third time that ICANN rejected the proposal. The agency tabled and effectively rejected a similar proposal in 2000 out of fear the “.xxx” domain would force the body into content regulation.

ICM resubmitted its proposal in 2004, this time structuring it with a policy-setting organization to free ICANN of that task. But many board members worried that the language of the proposed contract was vague and could kick the task back to ICANN. The board rejected the 2004 proposal last May.

ICANN revived the proposal in January after ICM agreed to hire independent organizations to monitor porn sites’ compliance with the new rules, which would be developed by a separate body called the International Foundation for Online Responsibility.

ICM revised it again a month later to clarify ICANN’s enforcement abilities and to underscore the independence of the policy-making body.