The US body which oversees the workings of the internet is being challenged over its handling of the .com domain.
The .com domain is highly prized
The row concerns the decision by the Internet Corporation for Assigned Names and Numbers (Icann) to allow the private firm Verisign to maintain control of .com forever.
A trade body for internet businesses says the deal between Icann and Verisign breaks US anti-trust laws.
It has filed a lawsuit against the two parties in San Jose, California.
The latest legal twist over the .com domain comes a month after Icann and Verisign settled a long-running legal dispute.
The dispute was over a controversial search service by Verisign called Site Finder.
The service meant if web users were looking for a .com or .net domain that did not exist, they were sent to Verisign's website instead of just getting an "error" page.
The issue was settled in October, with Verisign agreeing to a formal review process for new services which gives Icann 90 days to raise any concerns.
Under the terms of the agreement, Verisign had its contract to maintain the database of 35 million .com domain names extended from 2007 to 2012.
But details of the agreement suggest that the contract will be automatically renewed after that date, unless Verisign goes bankrupt or materially breaches the agreement.
The lawsuit filed by the World Association of Domain Name Developers alleges the deal creates a monopoly of the .com market.
The agreement "provides for the automatic renewal of the agreement and thereby precludes competitors from ever entering the .com and .net domain name registration market", said the filing.
The filing also accuses the two sides of price-fixing, arguing that the deal allows Verisign to raise prices at double the rate of inflation.
In a statement, Icann said the lawsuit was designed to overshadow its current meeting in Vancouver.
"Icann is currently seeking public comments and comments from its various industry and stakeholders groups on a proposed Verisign and Icann settlement arrangement
announced on 24 October 2005," said the statement.
"The lawsuit appears to be an effort to divert the Internet community discussions
during the Icann meeting, to the issues raised by a specific industry sector."
California-based Verisign declined to comment on pending litigation.