LONDON (Reuters) - British oil company BP Plc pleaded guilty on Thursday to criminal charges relating to its 2010 oil spill and agreed to pay an extra $4.5 billion on top of the tens of billions it is already paying out.

BP said it would plead guilty to 11 felony counts of misconduct or neglect relating to the death of 11 workers, one misdemeanor count under the Clean Water Act, one misdemeanor count under the Migratory Bird Treaty Act, and one felony count of obstruction of Congress.

(Reporting by Andrew Callus; editing by Ben Hirschler)