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                                                                    EXHIBIT 23.1
    
 
   
               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
    
 
   
     We consent to the reference to our firm under the caption "Experts" and to
the use of our report dated March 8, 1999, with respect to the consolidated
financial statements and schedules included in Pre-Effective Amendment No. 2 to
the Registration Statement (Form S-3 No. 333-70885) and related Prospectus of
Global TeleSystems Group, Inc. dated on or about April 16, 1999.
    
 
   
                                            /s/  Ernst & Young LLP
    
 
   
Vienna, Virginia
    
   
April 14, 1999