ACCORDING TO THE PLT, NO ICING PIREPS OR SIGMETS WERE RECEIVED DURING HIS PREFLT WX BRIEFING. HOWEVER, THE NWS BRIEFER STATED THAT HE TOLD HIM OF ONE PIREP & ONE SIGMET CONCERNING ICING THAT AFFECTED HIS PROPOSED ROUTE OF FLT. EN ROUTE TO HIS DESTINATION, THE PLT HAD TO DIVERT DUE TO LOW CEILINGS. HE THEN BEGAN TO NOTICE ICE ON HIS WINGS AS HE FLEW THRU HEAVY RAIN. HE BEGAN AN INSTRUMENT APPROACH WITH A ONE INCH BUILDUP OF ICE. AS THE ICING INCREASED, HE USED FULL POWER TO MAINTAIN A SAFE SPEED MARGIN. OVER THE APPROACH LIGHTS, HE REDUCED POWER SLIGHTLY & LOWERED THE GEAR. THE AIRSPEED DROPPED RAPIDLY & THE LEFT WING STALLED. SUBSEQUENTLY, THE ACFT IMPACTED A SNOW BANK APRX 40 FT SHORT OF THE RWY & WAS DAMAGED. AN EXAM OF THE ACFT REVEALED A ONE INCH THICK LAYER OF MIXED RIME & CLEAR ICE ON THE LEADING EDGES OF THE WINGS & TAIL SURFACES.