Webb is moving to the Kellogg's Innovation team as senior innovation manager for kids' snacks from this month.
She leaves a team of six in the promotions department following two-and-a-half years in the role of consumer promotions controller under marketing operations and media controller David Walker.
A Kellogg's spokesman said the cereal giant was continuing to look for the best candidate and no appointment had yet been made to replace Webb.
The move comes a month after the release of P&I's Licensing Leaders 2006: The Top 20 list which saw Webb ranked fourth for her award-winning work on the Horrible Histories audio CD promotion and Pirates of the Caribbean and King Kong link-ups. Webb was credited with raising Kellogg's promotions game.
Meanwhile, forthcoming work for Kellogg includes sampling activity in the New Year to support the expansion of its heart health Optivita range, which saw berry and raisin bars following the launch of the cereal earlier this year. Kellogg forecasts it will give away 400,000 bars during a month's "bar in box" sampling activity.