Internet voice service provider Jajah on Thursday said that web auctioneer eBay blocked the use of the startup's embedded voice links on its auction site, a move Jajah said raises concerns about anti-competitive behavior.

Jajah said eBay removed the listings of sellers who used Jajah’s technology, which enables potential buyers to connect with sellers through a click-to-call button embedded in their ad.

eBay sent emails to its sellers in the U.S. and Italy instructing them that Jajah’s technology, called Buttons, violated eBay’s link policy.

eBay’s policy seeks to protect its site from unauthorized or insecure links that could harm its business, but Jajah charges that eBay’s ownership of Skype, a VoIP firm, makes the auction giant’s argument specious.

“The fact that eBay acquired Skype for billions of dollars showed that they thought that VoIP would be a value-add for its community,” said Roman Scharf, co-founder of Mountain View, California-based Jajah. “Now that we are offering VoIP to the eBay community, eBay finds it to be a problem.”

According to Mr. Scharf, eBay, which acquired Skype in October 2005 for $2.5 billion, is pursuing the no-Buttons policy in the U.S. and Italy but not in other markets such as Germany and the U.K.

San Jose, California-based eBay said Jajah’s Buttons violates its links policy in every country in which eBay does business, and that it will continue to remove listings that include Jajah’s Buttons.

“We don’t allow Skype buttons in our listing pages either,” said Catherine England, an eBay spokeswoman.

“There are Skype links in specific areas and we have started testing Skype buttons but anytime a link directs users off of our site, it creates opportunities for fraudsters,” Ms. England said. “The policy is about safety for our members.”

Jajah’s Buttons, introduced on Monday, allow sellers for instance to place widgets in blogs or emails and have potential buyers make an inexpensive calls to sellers without the seller giving out his or her phone number.

“eBay’s policy makes reference to insecure or political content and the like, and our Buttons are nothing like that,” Mr. Scharf said. “We don’t take the user to a rival or fraudulent site or any such thing. Using Buttons just means that the user’s phone rings.”

Mr. Scharf said he is willing to offer eBay a commercial olive branch – a piece of the action.

“Every single Jajah call means money in the pocket of our partners,” he said. “eBay has its choice. It can simply tolerate Jajah or support Jajah but either way it will mean revenue for them.”

With VoIP application providers increasingly embedding voice communications in emails, blogs and web sites, it seemed inevitable that some Internet business would eventually move to block non-sanctioned VoIP services.

But the fact that the web business is eBay, which owns Skype, the best known VoIP provider in the world, brings up issues of open markets and competition that could draw regulatory attention.

VoIP sits on a precarious boundary between the Internet and telecommunications. On the one hand, the Internet is cheered as the ultimate open marketplace. On the other, telecommunications is one of the most heavily regulated industries in the world.

“Once voice becomes an application embedded in a web page, the notion of utility telephony begins to crumble,” said Will Stofega, an analyst with IDC. “Of course, if there is a compelling advantage or difference between clients, that may change the game and an end user may demand their favorite client.”

If eBay users challenged the auction site’s policy, then the issue could get on the U.S. Federal Communications Commission radar, said Mr. Stofega.

“But at the end of the day, I bet neither of the parties want that,” he concluded.