-By Andrew McMains and Noreen O'Leary, Adweek

Interpublic Group confirmed today that Mediabrands CEO Nick Brien will succeed John Dooner as worldwide CEO of Interpublic Group's McCann Worldgroup.

Brien, 48, will also assume Dooner's secondary role of CEO at McCann Erickson. The succession takes effect April 1, with Dooner, 61, remaining as chairman until the end of the year.

In statement, IPG CEO Michael Roth said, "We wanted to be sure that the selection of new leadership was implemented as thoughtfully and thoroughly as possible. This will ensure that the agency's future lives up to its storied place in the history of our industry. With the guidance of the board and John's active participation, I am confident that we have considered the most comprehensive slate of candidates."

Roth said that Brien has "accomplished great things since joining us to lead UM a few years back -- we are all in agreement that he is a terrific choice to lead McCann at this vital time of change and opportunity in media and marketing."

As to Dooner, Roth said: "John built the Worldgroup and has in recent years helped revitalize its offerings across multiple marketing disciplines." Roth said Dooner would be "totally focused" on the transition through the end of the year. Beyond that, he said, "we will look for opportunities to continue tapping into John's unique range of experience as an advisor on global advertising matters."
 
In an internal memo obtained yesterday by Adweek, Dooner described his successor as the "ideal choice to lead the multi-disciplinary Worldgroup," which includes McCann, Universal McCann, MRM Worldwide, Momentum and Weber Shandwick, among other units.

Brien "loves the business, and has the needed energy, willingness, humor, passion and involvement to do the job," Dooner added. "He believes, as I do, that when our clients succeed, we succeed. And he is relentless."

The selection concludes a search process that began in 2007.

This was Dooner's second tour as Worldgroup CEO. He returned to the post in February 2003 after David Bell replaced him as chief executive of the holding company. Dooner assumed the top job at IPG in December 2000, after eight months as president and chief operating officer.

His tumultuous run as CEO of the holding company was cut short amid an investigation into a $181.3 million accounting imbalance that stemmed chiefly from the overbooking of revenue across different offices of McCann in Europe. The Securities & Exchange Commission launched a probe of the imbalance in 2002 that was settled in 2008 when McCann agreed to pay a civil penalty of $12 million.

Brien, a U.K. native, entered the IPG fold in August 2005, when he became president and CEO at UM. Before that, he was CEO of Publicis Groupe's Arc Worldwide.

Earlier, he was president of corporate business development at Starcom MediaVest Group and CEO of Leo Burnett in London. He began his career in London at Grey in 1982, and joined Burnett in 1992 as executive media director.

Brien assumed his current Mediabrands role in July 2008. In that capacity, he oversaw the global media networks UM and Initiative; centralized negotiation entity Magna and media barter group Magna Trading; dedicated Johnson & Johnson agency J3; diversified agencies NSA, OSI and Wahlstrom; marketing accountability specialist MAP; and the Emerging Media Lab.

Dooner, who first joined McCann in 1984 after more than a decade at IPG's Marschalk, said in his memo that he is "enormously proud of McCann Worldgroup's record of success and innovation, and the extraordinary contributions that each of you has made to that success. Just 12 years ago, Worldgroup was a concept. Today it is ranked as the largest marketing communications company in the world." --with Steve McClellan

This story updates an earlier item with IPG's confirmation and additional details.