The UN Office for Disarmament Affairs (UNODA) provides support to the disarmament bodies created by the General Assembly and the Security Council and generally promotes disarmament efforts.
UNODA was established by General Assembly resolution 61/257 of 15 March 2007, as a successor to the Department for Disarmament Affairs (DDA).
A complete history can be found in Chapter 4 of The United Nations and nuclear orders (link to ebook for UNHQ)
UNODA publishes The United Nations Disarmament Yearbook since 1946