Socitm's chief executive, Kate Mountain, has resigned from her post.
The Society of Information Management announced her decision to leave on Friday. Mountain resigned with immediate effect but will continue in a consultative role until March.
Her timing means the society will be able to put new management arrangements into place as it ends the first stage of a corporate review, which aims to identify which services the society should provide and how they should be delivered.
Socitm said it followed a series of other reviews conducted during 2007 to shape the Society's activities for its next stage of development.
It said in a statement, "The society is in a period of intense change stimulated by the growing importance of ICT within the public sector efficiency and customer service agendas."
Kate Mountain said, "It has been my intention for a while to move to a new challenge, but I was keen to see the service review programme substantially complete and now that the corporate services review is in full swing I feel it to be an appropriate time to go."
She joined Socitm in 2002 following a career in public sector IT, which included being head of IT at Liverpool and Oxford City Councils.
Rose Crozier, Socitm president, said, "During Kate's tenure the Society has seen a significant increase in membership, services and activity, and also in Socitm's influence on national policy for local and central government IT."