Rob Hayward, the chief executive of the British Beer and Pub Association (BBPA), is to leave the trade body with immediate effect after 10 years in the role.
Explaining the shock move, Hayward said he wanted to more "actively pursue" his political interests.
The BBPA has agreed to release Hayward with immediate effect, although he will be assisting in the transition process until his replacement is identified.
In a statement, the trade body said: "The BBPA would like to place on record their thanks for his contribution to the success of the association and wish him well as he embarks upon this new challenge."
Hayward has been at the forefront of the pub industry's dialogue with the Government on issues such as licensing reform, the smoking ban and alcohol duty.
By Daniel Thomas
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