De Jong, who will transfer from Campina's head office in the Netherlands, has been tasked with driving Yazoo forward and strengthening Campina UK's position in the flavoured milk category.
The Grocer's Top Products Survey 2008, published last month, revealed sales of Yazoo rose 3.5% to £28.3m in the year to 4 October. It was the second-biggest brand in the flavoured milk category, trailing behind Dairy Crest's Frijj, which chalked up a 19.1% rise in sales to £36.1m during the period.
Campina UK has moved to close this gap, introducing new packaging for Yazoo in October and adding real fruit juice to its strawberry and banana flavours for the first time.
"We are entering a challenging time for brands, but I am looking forward to continuing to grow the Yazoo brand throughout 2009 and beyond," said de Jong, who will be responsible for all UK marketing activity for Yazoo, as well as the company's range of own-label products.
De Jong was previously responsible for Campina's cream division. In this role she introduced a new range of culinary cream products and increased the company's market share in cream from 36% in 2006 to 44% in 2008. She has also worked for Philips and Sara Lee, in both Russia and Holland.
"Marielle's past experience and extensive product knowledge will be important to our continued success in the UK market," said John Lee, managing director of Campina UK.