EBay, the internet auction site, effectively hoisted the “For Sale” sign on Skype on Tuesday night when it announced plans to spin off the revolutionary internet calls business in an initial public offering some time next year.

Four years after paying $3.1 billion for Skype, eBay conceded that its ambitious plans to harness the new technology to boost its core auction business by enabling buyers and sellers in its online marketplace to talk had run into the ground.

Analysts said that the move opened the door for any private equity buyers to move in on the calls company.

It leaves open the possibility that the creators of Skype, the billionaire Scandinavians, Janus Friis and Niklas Zennstrom, could repurchase the company. The pair have been plotting with a quartet of private equity groups including Warburg Pincus to seize back the business they founded.

John Donahoe, the chief executive of eBay, said: “Skype is a great stand-alone business with strong fundamentals and accelerating momentum. But it is clear that Skype has limited synergies with eBay. We believe operating Skype as a stand-alone publicly traded company is the best path for maximising its potential.”

EBay's plans were cheered by investors, who sent the shares up 56 cents, or 3.9 per cent in after-hours trading on Wall Street. They saw Skype as an unnecessary distraction that was tying up capital.

Skype revolutionised the calls market and dealt a blow to traditional phone companies when it launched its software, which offers free or cheap calls over the web. After two years of breakneck growth the company was snapped up by eBay.

In 2007 eBay, which is being advised by Goldman Sachs, conceded it had massively overpaid for the calls company when it took a writedown of $1.4 billion. Last year Skype generated revenues of $551 million, up 44 per cent from 2007. Its user base - now at 405 million - leapt 47 per cent from 2007.

A recent release of Skype for iPhone generated a strong response. More than one million people downloaded the software in the first 36 hours after it became available.

Mr Zennstrom and Mr Friis used the money from the buyout to set up a venture capital group, and were early investors in Joost, the video-sharing site.

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