CLOSE PROX ACR-MLG GA-SMA IN TRAFFIC AT CMH.

Narrative

WE WERE CLRED FOR A VISUAL APCH TO RWY 10R AT COLUMBUS FROM A POS ON A RIGHT DOWNWIND LEG. AS WE BEGAN THE TURN TO FINAL AT APPROX 2500' MSL THE TWR CALLED OUT POSSIBLE TFC AT 12 O'CLOCK IN THE TURN; WHICH WAS A LIGHT ACFT MANEUVERING FOR A VIS APCH TO RWY 05 AND APPARENTLY NOT FOLLOWING THE TWR'S INSTRUCTIONS. WE DID NOT PICK UP THE TFC AFTER THE FIRST CALL AND ASKED TWR TO KEEP US ADVISED. AFTER THE SECOND ADVISORY; THE F/O ACQUIRED THE TFC AND WE INITIATED AN IMMEDIATE LEFT TURN TO AVOID A COLLISION. AFTER AVOIDING THE IMMEDIATE THREAT WE RESUMED THE APCH AND LANDED UNEVENTFULLY. AFTER PARKING AT THE GATE I TELEPHONED THE TWR TO RELATE WHAT HAD HAPPENED AND GET THE TAIL # OF THE LIGHT ACFT. IT WAS AT THIS TIME THE CTLR EXPLAINED HOW THE LIGHT ACFT WAS NOT WHERE HE WAS SUPPOSED TO BE. AS I UNDERSTOOD IT; HE WAITED AN EXCESSIVE AMOUNT OF TIME TO CONTACT TWR AFTER THE HDOF FROM APCH. HE WAS THEN TOLD TO PROCEED SBND (TO STAY OUT OF OUR PATTERN) BEFORE TURNING BASE FOR RWY 05. INSTEAD HE CONTINUED INBND TO THE FIELD. FLEW THROUGH OUR FLT PATH; AND THUS CREATED A NEAR COLLISION.