In comments broadcast today on BBC radio, Ashdown said there was no peace without justice and expressed frustration that Bosnian Serb wartime leader Karadzic and his main military commander Mladic remained at large.
Both are wanted by the UN war crimes court at The Hague for genocide and crimes against humanity.
Ashdown, who has held his post since 2002, is due to step down as the UN high representative in Bosnia at the end of this year.
He is to be replaced by former German cabinet minister Christian Schwarz-Schilling.
Coffins of Srebrenica victims being prepared for burial in October (AFP)
THE WORST ATROCITY IN EUROPE SINCE WORLD WAR II: The July 1995 massacre of some 7,000 Muslim men and boys by Bosnian Serb fighters near the UN-designated safe haven of Srebrenica is the worst atrocity of its kind in Europe since the end of World War II. Since the incident, the name Srebrenica has become practically synonomous with ethnic cleansing....(more)