The U.N. copyright agency that arbitrates more than half the world's "cybersquatting" cases saw a 25 percent increase in complaints last year.
The World Intellectual Property Organization received 1,823 complaints in 2006 alleging abusive registrations of trademarks as Internet domain names.
The complaints came mainly from information technology, financial and pharmaceutical companies, as well as famous fashion brands and the entertainment industry.
The growing number of professional domain name dealers who use computer software that automatically registers expired domain names or temporarily registers them without paying charges, is of concern to trademark owners, WIPO said.
"Domain names used to be primarily specific identifiers of business and other Internet users, but many names nowadays are mere commodities for speculative gain," said WIPO's deputy director-general, Francis Gurry.
Most of last year's disputes have been resolved, including cases brought by Tamiflu maker Roche Holding AG, Wal-Mart Stores Inc. and America's Cup-winning sailor Russell Coutts.
Anyone can register a domain name for as little as a few dollars. The arbitration system, which started in 1999, allows those who think they have the right to a domain to claim it without a costly court battle or payment of large fees to buy the name.
But critics say the system favors trademark holders and not individuals who also may have legitimate rights to the names for parody, criticism and other purposes.
Since 1999, WIPO has decided in favor of the complainant in 84 percent of all cases.