Vodafone Group PLC's stock plummeted 5.59% in pre-market trading on Tuesday, as the telecommunications giant grappled with a sharp revenue decline in its key German market, offsetting growth in other regions.

The company reported a 7.6% drop in revenue in Germany for the third quarter, its biggest market accounting for 34% of group service revenue. Service revenue in the country fell 6.4% to €2.89 billion, partly due to the impact of regulatory changes that prevent landlords from bundling TV services with rental agreements, as well as a lower broadband customer base.

CEO Margherita Della Valle acknowledged that the turnaround in Germany will take time, as the group absorbs the impact of the law change and faces a highly competitive market environment. Vodafone's struggles in the country overshadowed positive performance elsewhere, including a 3.3% organic growth in UK service revenue, boosted by investments in customer experience.