Martin Sorrell, chief executive officer of WPP group. (Brendan McDermid/Reuters)

Glover Park Group, the Washington communications and government relations firmannounced Tuesday that it is being sold to London-based marketing giant WPP.

Glover Park Group was founded in 2001 by four Democratic insiders from the Clinton White House and 2000 Al Gore presidential campaign. It has annual revenue of about $60 million. The firm has 140 employees and offices in New York, Los Angeles and Boulder, Colo., in addition to its Washington headquarters.

WPP, the world’s largest communications services group, has annual revenue of roughly $15 billion and employs 153,000 people in 2,400 offices in 107 countries.

The transaction is subject to regulatory approval. The purchase price was not disclosed publicly.

Both firms said there are no anticipated changes to Glover Park’s leadership structure or staffing.

“All founding partners other than Joe Lockhart [the former Clinton spokesman who departed for Facebook in June], are here for the foreseeable future,” said managing director Jason Miner. “There will be no changes in the way firm is run day to day.”

Miner said WPP will give Glover Park a global platform on which to grow, but said there are no specific plans to expand internationally.

Glover Park brought in nearly $6 million in lobbying revenue last year, advocating for clients including Blue Cross/Blue Shield, General Electric, the NFL, News Corp., Pfizer and Toyota.

WPP already owns several government affairs firms: Quinn Gillespie, Wexler & Walker, Public Strategies Inc., Ogilvy Government Relations, Prime Policy Group, Dewey Square Group, Hill & Knowlton and Burson-Marsteller.