Chairman of the BBC Trust Rona Fairhead is to step aside after two years in the role, the organisation has confirmed.
In a statement Ms Fairhead said she decided to quit rather than take part in the reapplication process for the role.
She said: "The Prime Minister strongly encouraged me to take part in the new appointment process, for what would be a new four year term as BBC chairman.
"However, after much thought I have come to the conclusion that I should not do so.
"It is my belief that it will be better to have a clean break and for the Government to appoint someone new, and for me to continue my career in the private sector as I had always planned to do after my existing term ended in 2018."