Martyn Thomas has left the Rugby Football Union with immediate effect, with Stephen Brown taking over as acting chief executive.
Thomas had announced his intention to leave the RFU on 16 December but his departure has been brought forward.
The former RFU chairman is also leaving as chairman of the organising committee for the 2015 World Cup in England.
"Stephen has shown in the time that he has been at the RFU that he is immensely capable," said Thomas.
"This has been underlined once again in the last few weeks.
"It is therefore entirely logical that he takes on the role of acting CEO as soon as possible. He is highly respected by the staff and I have every confidence that he will provide the stability and leadership needed until a new permanent CEO takes office."
Thomas survived a vote of no confidence in September after threatening legal action should a report by judge and RFU disciplinary officer Jeff Blackett into the exit of predecessor John Steele be made public.
Blackett's report was critical of Thomas, 67, who faced the prospect of a misconduct charge before being told on Tuesday that he had no case to answer.
Brown was chief financial officer of the RFU before taking over his new role earlier this month.
RFU chairman Paul Murphy said: "Our thanks go to Martyn for all the time and effort he has invested on behalf of the RFU in England over the years. Much credit in particular must go to him for the decision to award England the hosting of the Rugby World Cup in 2015.
"I have said before that Stephen Brown is a great asset to the Union and we have every confidence that he will have a positive influence during this transitional period until the new CEO takes office."