Amanda Walsh, the Red Cell Europe chief executive, is talking to Robertson with a view to him taking his new job within the next two weeks.
It is unclear if a deal would involve Red Cell buying Red Spider, the virtual planning agency Robertson, a former planning director at Bartle Bogle Hegarty and The Leith Agency, set up in 1995.
He is expected to divide his time between London and New York and act as a bridge between Walsh and Andy Berlin, Red Cell's chairman.
Senior executives are understood to believe they need to strengthen their planning expertise if Red Cell is to be a serious global player to rival other micro-networks.
Sources say the move has been sparked in part by Red Cell's relationship problems with Headlight Vision, its new product development and marketing consultancy.