Paul Hammersley, the chief executive of Lowe Lintas, is leaving the London agency to become the chief executive of its New York office.
It is understood that he is also being considered as the chief executive for the network's North American division, although the decision has not been finalised.
Chris Thomas, the existing managing director, will replace Hammersley as the chief executive in London. However, he will report to a group chief executive - a new role for the group as yet unfilled.
It is thought that Jeremy Bowles, the client services director, will be promoted to the role of managing director.
The news will end the rumours that Hammersley was considering taking a senior role at Young & Rubicam in New York.
Hammersley is a well regarded figure in UK advertising, having bedded down the merger of Ammirati Puris Lintas with Lowe Howard-Spink at the end of 1999 and going on to win accounts such as Orange. The agency was Campaign's Agency of the Year for 2000.
Hammersley joined Lowe in 1993 when he left Saatchi & Saatchi to become the executive vice-president of Lowe Group North America - reporting to the network's founder, Frank Lowe.
He remained in New York for four years where he became the worldwide co-ordinator on the Coca-Cola account, before returning to the UK to take up the managing director role at Lowe Howard-Spink in 1997. He became the chief executive in November 1999 after the merger with APL.
Chris Thomas was the chief executive of APL before becoming the managing director of the merged agency.
Hammersley's move is expected to take place this summer. He will replace Lee Garfinkel, the chief executive in New York, who is leaving the agency after only seven months in the role.
Garfinkel, who was the chief creative officer in New York for eight years, has an offer to stay within IPG - running his own boutique.
Since the merger, the New York office has been underperforming: Sun Microsystems, Denny's, Burger King, KPMG and Unilever's Mentadent have all quit the agency. However, more recently it has won five new pieces of business from clients including Bestfoods and General Motors.
Interpublic sources refused to confirm the story.