-By David Gianatasio, Adweek

In an unexpected move, Aegis Group today said its chief executive, Robert Lewill, would exit his post at month's end.

John Napier, who serves as chairman of the U.K.-based marketing and media company, will take on his responsibilities on an interim basis.

In a statement today, Napier said: "The strength of Aegis is the performance of its two large international businesses, Aegis Media and Synovate. They are both well managed and we expect their combined 2008 operating results to be broadly in line with the average of current market expectations. The ongoing priorities involve working closely with both companies to ensure that we are in the best possible shape to meet the challenging conditions ahead and ensuring that we also continue to focus on providing a range of services."

He thanked Lerwill for his contributions to the firm's growth since the latter became chief executive in early 2005.

In the same statement, Lerwill said: "I have enjoyed my time at Aegis. I leave the group in good hands, with a strong management team capable of meeting the demands of the future. I wish them every success."

For most of his tenure as CEO, Lerwill found himself enmeshed in efforts by Havas chairman Vincent Bollore to win seats on Aegis' board. Bollore, who is also the single largest shareholder in Aegis, failed in five such attempts, which were opposed by Aegis management based on conflict of interest issues.

Bollore has wanted to combine Havas' MPG media operation with Aegis' capabilities -- but as yet no deal has come to fruition.

The firm was stung a few weeks ago when one of its key accounts, Renault-Nissan, shifted some $750 million in media business to Omnicom Group's OMD from Aegis' Carat.

Caught up in the global economic malaise, Aegis' shares have lost about half their value since September, though they rose more than 15 percent by late afternoon on Thursday, London time, following the announcement that Lewill would exit.

There's been already been lots of change this year at Aegis, with Aegis Media EMEA chief Jerry Buhlmann succeeding Mainardo de Nardis in the spring as global CEO of Aegis Media. (De Nardis later joined OMD in a senior role.) David Verklin, chief executive of Aegis Media Americas, also departed this year.