The deposed Bundesliga champions have promised to invest heavily over the summer after failing to even qualify for next season's Champions League.

And after already clinching the signatures of Hamit Altintop from Schalke, Jose Ernesto Sosa from Estudiantes de la Plata and Aachen's Jan Schlaudraff, Jansen is the latest but not the final piece in the puzzle.

"I am really delighted about this true strengthening (of the squad)," said Bayern coach Ottmar Hitzfeld.

Jansen, 21, has signed a four-year deal with the Bavarian outfit for an undisclosed fee, but he was quick to praise his former club.

"I thank Borussia for respecting my wishes and allowing me to move," said Jansen who can play in midfield and defence.

"I have a lot to thank them for and I will keep my fingers crossed they return to the Bundesliga as soon as possible."