LONDON, Oct 24 (Reuters) - G4S GFS.L , the world's biggest security services firm, said on Thursday its UK chief executive Richard Morris has resigned and has been replaced by the group's chief operating officer Eddie Ashton.

Morris leaves at a time when the group is trying to recover from a series of damaging setbacks with the British government, one of its key clients, the latest being the discovery that it and rival Serco SRP.L had charged for tagging criminals who were either dead, in prison or never tagged in the first place.

That discovery has prompted the government to ask the Serious Fraud Office to consider carrying out an investigation into G4S. Britain has also put all contracts held by the firm under review. ID:nL6N0FH2CQ

Morris had been with G4S for 10 years while Ashton joined as COO from Deutsche Post DHL DPWGn.DE in July.

Morris's departure is the second for the UK division in just over a year after David Taylor-Smith left the firm following its failure to supply enough security guards for the 2012 Olympic Games.

(Reporting by Neil Maidment; Editing by Greg Mahlich)

((neil.maidment@thomsonreuters.com)(+44 0 207 542 2292)(Reuters Messaging: neil.maidment.thomsonreuters.com@reuters.net))

Keywords: G4S UK/