LONDON—Facebook has ended its four-year relationship with the UK's Nelson Bostock, calling in Edelman to oversee PR for its B2B business. 

Facebook UK and Ireland head of PR/communications Sophy Tobias confirmed the development, which sees Edelman assume PR duties for the social networking giant's advertising, product and platform units.

The move comes as eMarketer forecasts that Facebook UK's advertising revenues will reach £300m in 2013, up 36 percent on its 2012 earnings in the market. The digital platform's outreach to advertisers and agencies forms a critical element of its B2B proposition, particularly as it expands its mobile advertising services.

Nelson Bostock MD Lee Nugent told the Holmes Report that it was the "right time for both the agency and the client to move on to other things."

Facebook will continue to work with corporate/public affairs lead Blue Rubicon, a relationship that began in 2010.