The factor of safety against sliding is defined as the resisting forces (friction and passive forces) divided by the driving lateral force. 
As per IS Code 1904: 1986, the minimum allowable factor of safety against sliding for a cantilever retaining wall should be 1.50 when dead load, live load, earth pressure are considered together with either seismic forces or wind forces. 
However, in above case, if effect of wind force or earthquake forces is not considered then factor of safety is taken as 1.75 against sliding. 
Note: The minimum allowable factor of safety against overturning shall be 1.50, when dead load, live load, earth pressure are considered together with either seismic forces or wind forces. However, in above case, if effect of wind force or earthquake forces is not considered then factor of safety is taken as 2 against overturning.