Plans to create an internet domain specifically for pornographic websites have been rejected.
The Icann board rejected the proposal nine votes to five
The proposal for the .xxx domain was voted out by the overseer of the net's addressing system, seven years after the ideas was first put forward.
Board members said they were concerned that approval would put the agency into the position of a content regulator.
Backers of the .xxx domain said they were disappointed by the decision and would pursue the matter further.
It is the third time that the Internet Corporation for Assigned Names and Numbers (Icann) has rejected the bid.
The idea of creating a net domain for pornography was first floated in 2001 and was given approval in June 2005 by Icann which oversees the net's addressing system.
Final approval was scheduled to take place in December 2005 but this was delayed until May 2006 when the proposal was abruptly dropped over worries about how sites signing up to use .xxx would be policed.
At the time, ICM Registry - the backer of the .xxx scheme - gave pledges that it would ensure sites signing up did not hit users with spam or spyware.
ICM also had to give assurances that it would put in place systems to prevent children seeing the sites and that no .xxx sites would contain images of child abuse.
A final decision on the domain name was taken at a meeting of board members in Lisbon, Portugal.
It was rejected by nine votes to five. Paul Twomey, Icann's chief executive abstained from the vote.
"This decision was the result of very careful scrutiny and consideration of all the arguments," said Dr Vinton Cerf, chairman of Icann. "That consideration had led a majority of the board to believe that the proposal should be rejected."
Many on the board voted against the proposals because they felt that accepting the domain would mean Icann would be seen as a regulator of content, deciding what is pornographic and what is not. This was not the role of the agency, they argued.
"My decision turned on one point and one point only," board member Steve Goldstein told Associated Press.
"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."
Others, who backed the schemes, said that content could be managed by local and national laws.
"We are extremely disappointed by the board's action today," Stuart Lawley, ICM's president and chief executive told Associated Press. "It is not supportable for any of the reasons articulated by the board."
ICM Registry argue that a .xxx domain would act as a quality control for the industry and would allow individuals and families wishing to avoid adult content to easily filter it.
Critics have pointed out that use of the .xxx domain is entirely voluntary and some suspect that few sites would sign up to use the suffix.
Icann said it would not take any more proposals for so-called top level domains like .xxx at the moment, but did not rule out more in the future.