FDA general secretary Jonathan Baume has announced his retirement from 31 October 2012.
He said it was a test of a chief executive and leader to know when to step aside, and that, after almost 15 years as FDA general secretary, " it feels the right time - both personally and for the organisation - to begin preparations to hand over to a successor".
He added: "I will continue to lead the FDA in the difficult and complex negotiations to reach agreement with the Government on revised pension arrangements for civil servants. We are now making genuine progress but considerable work remains.
"Further major challenges confront civil servants and the public services more generally, as people and organisations adapt to what is likely to be a decade of austerity. Substantial reforms are inevitable and those are best addressed for the FDA by a general secretary with a full term ahead of them."
Sir Gus O'Donnell, cabinet secretary and head of the civil service, said that Jonathan had "worked tirelessly and very effectively to represent his members, and over many years his honest, objective approach has earned my trust and respect".
The FDA has the coming ten months to select a new general secretary, hold the statutory election required and conduct a transition. A public competition to select a successor will be launched in January.
Jonathan was first elected FDA general secretary in early 1997 and was re-elected in 2002, 2006 and 2010. He is currently the longest-serving union general secretary in the UK. A biography can be read here.
Baume: 'the right time' to begin preparations to hand over to a successor.