Harding has been named general manager for GSK Consumer Healthcare Ireland.
The incumbent in Dublin, John Sayers, has been moved to general manager for GSK's Consumer Healthcare business in Central and Eastern Europe.
A spokesman for GSK said recruitment for Harding's successor was under way.
Harding joined GSK in 1997, since when Lucozade's UK sales have grown by 60%. He was previously a senior marketer at Scottish Courage, where he introduced Jack Dee and his penguins to John Smith's advertising.
The new job will be Harding's first general management role and extend his remit to GSK's oral care and OTC brands, including Beechams, Aquafresh and NiQuitin CQ.
"This will allow me to develop my knowledge and experience. It demonstrates that marketing can be a route to general management," said Harding.