Facebook has cemented its growing popularity by attracting a second senior executive from Google, the internet search engine giant, to help the social networking site to expand globally and develop its nascent advertising network.

Sheryl Sandberg, 38, currently vice president for global sales and operations at Google, will join Facebook this month as its chief operating officer after seven years at the online search engine company.

Ms Sandberg’s departure will be a blow to Google, which has lost a number of its vice presidents and senior managers in recent months, including the former chief financial officer at YouTube, the video sharing group owned by Google, who took the same role at Facebook.

While at Google, Ms Sandberg helped develop of two of its most important assets - the advertising platforms AdWords and AdSense, which deliver adverts to users of Google and other sites.

In hiring Ms Sandberg, Mark Zuckerberg, Facebook's 23-year old chief executive and co-founder, has elected to follow in the footsteps of Bill Gates, who retained the top role at Microsoft but took on external managers to help grow the company.

In contrast, Larry Page and Sergey Brin, Google's co-founders, chose to hand the reins of their company to an experienced manager when it underwent rapid growth in its early years.

Mr Zuckerberg said that Facebook, which has 38.5 million users worldwide, needs help with the task of becoming a major company, in particular with communication - a point that amplified last year when the company was criticised for introducing a feature that allegedly infringed on users' privacy.

The plan to allow brands to attach advertisements to messages sent between friends met with strong resistance from users.

Mr Zuckerberg, subsequently apologised for the way the system, called Beacon, was introduced, and made a commitment to respect Facebook users' privacy by allowing them to 'opt out' of the service.

"Communicating what we are about is clearly an important thing for us to do," he said.

Facebook, valued at around $15 billion, is now under pressure to convert its user base into revenues following a $240 million investment by Microsoft last year for a 1.6 per cent stake.

The company recorded sales $150 million last year, and is hoping to double that figure in 2008, its fourth full year of operation.

By comparison, Google's revenues in its fourth year were $440 million - a five-fold increase on the previous year.

Ms Sandberg joined Google three years before it went public, and like many long-time employees of the company is now a multi-millionaire.

In a statement, Omid Kordestani, a senior vice president for global sales and business development at Google, said: "Sheryl was a valued member of the Google team, and we wish her well in her new endeavours."

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