Artur Mas has headed Catalonia's regional executive since December 2010, when his centre-right Convergence and Union alliance defeated the Socialist Party of his predecessor, Jose Montilla, in legislative elections.
Relations between the central government and Barcelona have long been strained over issues such as devolution, distribution of revenues and local identity, and Montilla did not wish to serve up another pretext for raising tension between Catalonia and the rest of Spain.