Lee joined the London bid team at the end of 2003 and played a major role in securing the 2012 Olympic and Paralympic Games for London, working closely with bid chairman Lord Coe and chief executive Keith Mills.
Lee has no job to go to, but is said to be keen "to explore new professional opportunities" without shedding light on what these might be.
Lord Coe, 2012 chairman, said: "Mike has made a fantastic contribution to London 2012, particularly in positioning and communicating our plans to key audiences, including the media. I have enjoyed our time together and Mike thoroughly deserves his recent accolade as PR Professional of the Year."
Lee, who previously worked for Uefa and could be involved in any future Football Association bid for the World Cup, said the London 2012 campaign had been a great experience, with winning on July 6 the highlight of his professional career.
"I can not speak highly enough of the team we have built at London 2012 and now at the London Organising Committee. The sense of purpose and shared commitment between the bid team and all our supporters and stakeholders remains very special," Lee said.
Lee leaves London 2012 team on November 30 with Brock-Doyle taking up the post from December 1.
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