Motorola’s Chief Marketing Officer Kenneth Keller has left the company less than eighteen months after taking the job. According to reports, the company will not be directly replacing Keller. His former deputies, Eduardo Conrado and Jeremy Dale, will instead report to division presidents.

Mr Keller is the latest in a string of senior executives to leave the Schaumburg, Illinois-based group in the past year. In Dec, Motorola lost its CTO Padmasree Warrior, who joined Cisco Systems. The company is also now looking for a new head of the handset unit, a position currently managed by new CEO Greg Brown. Keller’s departure underlines ongoing problems at Motorola as Brown battles to return the mobile unit to profit and halt the slide in market share. Earlier this year the company admitted it was considering spinning off its mobile unit, following complaints by shareholders, including US billionaire financier Carl Icahn. Yesterday Mobile Business Briefing reported that Ichan has increased his stake in the company to 6.3%.