LONDON, July 20 (Reuters) - The struggling Swiss-based Sauber Formula One team announced a change of ownership on Wednesday and said investment firm Longbow Finance had signed an agreement to acquire Sauber Holding AG.

Team founder Peter Sauber will retire from all his functions, while Monisha Kaltenborn will remain as team principal and chief executive.

"It is Longbow Finance S.A.'s clear intention to stabilise the group and create the basis for a competitive and successful future," the team said in a statement.

"The transaction also secures the continuation of the brand Sauber in Formula One and will open opportunities to further grow the engineering activities of the group."

(Reporting by Alan Baldwin, editing by Ken Ferris) ((alan.baldwin@thomsonreuters.com; +442075427933; Reuters Messaging: Reuters Messaging: alan.baldwin.reuters.com@thomsonreuters.net))