Bebo, Britain’s leading social networking website, today announced a link-up with rival Facebook, which allows third-party software developed for one site to work easily with the other.

The link gives companies developing applications — including US television network NBC and music recommendation website Last.FM — the ability to write software that is compatible with both networks, which have nearly 100 million users.

Bebo’s decision is a boost to Facebook, which had stood apart from a competing standards initiative called Open Social. This is led by Google and supported by MySpace, the network owned by News Corporation, parent company of The Times. MySpace has 110 million users.

“Facebook had great success when it allowed third parties to write their own software applications a few months ago,” said Joanna Shields, the president of Bebo. “Now, within a few hours a Facebook application can run on Bebo, which should be good news for software developers”.

Facebook supports thousands of third party applications since it opened up its site six months ago. Those taking advantage of the technology include the BBC, which transmits all its stations via a digital radio player, or Britney Spears’ record label Zomba, which allows fans to get the singer’s music and video clips on their profiles.

However, the technical tie-up falls short of allowing people with Bebo profiles to link directly to Facebook users. “I don’t think we are there yet,” Ms Shields said. “We think people use social networks for different things: Facebook is a great social utility, whereas you use Bebo to share media and entertainment”.

Gap, the US clothing chain, is one of Bebo’s launch partners. Its software allows people to “cast themselves as Gap models,” according to Will Hunsinger, vice president and general manager of Gap Online, as the retailer tries to improve sales through online engagement.

Bebo, though, is also linking up with Open Social, as well as Facebook — making it the only major social network to straddle the competing technologies — which are known in the technology industry as “application programming interfaces” or APIs. That integration, though, will not take effect until “early 2008”.

Google set up Open Social at the end of October, and swiftly attracted the backing of MySpace. Despite MySpace’s greater size, Facebook’s early willingness to embrace third party development helped give it a boost that contributed to its massive surge in popularity this year. Facebook is now the clear number two worldwide, with around 50 million active users, just below half of MySpace’s level.

A year ago Facebook, which began life as a networking site aimed at US students, founded by college dropout Mark Zuckerberg, had 12 million active users. The growth, and excitement around the website, allowed it to raise $240 million from Microsoft on a valuation of $15 billion for the company.

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