According to insiders, Sky and Wieden & Kennedy parted company after just eight months due to disagreements over the creative direction taken on some ads. Sky declined to comment on the move.
BMB partner Trevor Beattie worked with Sky Networks managing director Dawn Airey on the relaunch of Five when Airey was its chief executive.
BMB's arrival will increase the pressure on HHCL United, which holds Sky's £60m brand business, as there has been speculation of a full ad review.
BMB handles the creative and strategic business for Sky News, which relaunched last month. It is expected to begin work on Sky One immediately. Sky has traditionally concentrated marketing spend on Sky One, but it may shift some to Sky Two and Three.
Last week, Sky revealed that it has 7.8m subscribers, an increase of 57,000 in the three months to the end of September.
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