More than half claim they have no time to plan for future business and short-term targets are distracting many from long-term success.
The findings from a study of almost 1,000 fleet managers show most blame the backlog on bureaucracy and attending too many meetings.
The report, which has been published by the Chartered Management Institute (CMI), also shows just 30% of managers “understand how their career will progress”.
However, despite difficulties with juggling their priorities, the majority of fleet managers (83%) look forward to being at work.
Jo Causon, marketing director at the CMI, believes companies need to do more to support fleet managers.
She said: “Organisations need to provide a supportive and open environment so individuals can dedicate time to developing fresh ideas.
“If UK employers fail to invest in the skills and competencies of individuals, there will be a serious impact on how well the UK performs in a global market.”