Launched at Switzerland's initiative on the 10th World Day against the Death Penalty, foreign minister Didier Burkhalter signed the appeal along with his counterparts from Germany, France, Liechtenstein, Austria and Italy.
"We intend to work together ... to ensure that the number of executions continues to decline, that judicial proceedings are made more transparent, and that further countries renounce the death penalty until this inhumane form of punishment has disappeared entirely," read the appeal, published in numerous European dailies.
More than 130 countries have abolished or put a moratorium on the death penalty but 50 nations continued to condone it, the statement said.
In a call to other nations to join the worldwide ban, the signatories described capital punishment as a practice "for which there can no longer be any justification in the 21st century.
"Killing in the name of justice is contrary to the fundamental values for which our countries stand," the appeal said, adding that in some cases "innocent people lose their lives."
In 2010, the UN General Assembly adopted, by 109 votes to 41, a third resolution on the moratorium on the death penalty.
This resolution -- coming after earlier proposals adopted in 2007 and 2008 -- was introduced by the six nations involved in Wednesday's appeal along with the European Union and numerous other countries around the world.
The UN General Assembly is to vote on the resolution again later this year to "secure an even greater majority in its favour," the signatories said.