Facebook is planning to launch a branded smartphone made by Taiwanese vendor HTC in mid-2013, according to sources at Bloomberg.

The 'Facebook phone' has been a long-standing industry rumour, but people with knowledge of the matter claim that plans have advanced following Facebook’s hiring of a number of former Apple engineers.

The team is focused on improving Facebook’s iPhone app and “developing a modified operating system for the [HTC] device,” the report says.

“We’re working across the entire mobile industry; with operators, hardware manufacturers, OS providers, and application developers to bring powerful social experiences to more people around the world,” was all Facebook would say in a statement. HTC declined to comment.

More than half of Facebook’s 900 million users access the social network via mobile devices, but Facebook currently generates little revenue on the mobile side compared to desktop. 

“Usage is shifting to mobile, and they have not been able to monetise mobile,” Victor Anthony, an analyst at Topeka Capital Markets, told Bloomberg. “To the extent that it’s a device you own and carry around with you at all times, and it ties into the Facebook experience, it will be beneficial. They could then put a lot of ads onto the platform.”

Facebook started offering mobile ads in March and could update on their impact in its second-quarter trading update due later today.

According to Bloomberg’s sources, the former Apple staff hired by Facebook include: Greg Novick, who helped develop the touchscreen user interface; Tim Omernick and Chris Tremblay, who also worked on the device’s software; and Scott Goodson, who helped create the stock-market application.