The police service requires "wholesale culture change" in order to respond to future financial pressures and questions over its legitimacy, according to a new report.
A review by the College of Policing found that "insular attitudes" among police officers acted a barrier to change and hierarchy and bureaucracy needed to be reduced.
While preventing crime and policing by consent remained the core duties of the service, its remit had "widened" to include protecting vulnerable people, in private public and online, the report added.
The Leadership Review authors said police culture had positive aspects including "decisiveness in difficult situations, compassion and care, a constant 'can-do' attitude".
But they added: "The nature of police work, including the presence of personal risk, can encourage a tendency to stick together in the face of threats and at worst, result in insular attitudes that inhibit change. The need for cultural change underpins many of the recommendations of this review and we should not underestimate what a challenge it will be to deliver.
"While wholesale culture change in any organisation is a long and demanding process, positive leadership can help to promote positive cultural traits that will, in turn, assist the police in adapting to a volatile and uncertain future."
A greater focus on "flatter structures" and emphasis on individual officer's discretion was needed, with ranks and grades possibly requiring reform.
The report made a total of 10 recommendations, including greater flexibility in career paths and entry points, increased diversity and a system to transfer more powers and legal authority to skilled staff.
"A failure to adapt and prepare for the future means there is a serious risk that the police service will falter under twin pressures of financial constraint and declining legitimacy," the report added.
Alex Marshall, College of Policing chief executive, said: "I do not underestimate the challenge of delivering these recommendations. While the college has a significant part to play, success in implementing the review requires a much wider response from across the police service, police and crime commissioners and the Home Office.
"Implementing the recommendations inevitably comes with a cost, but we accept that investment is crucial if we are to improve the way that our leaders are developed."
A recent report by the National Audit Office (NAO) concluded that forces in England and Wales do not have a clear understanding of the demands placed on them or the factors that affect their costs.
Central government funding for forces has been slashed by £2.3billion, or 25%, between 2010-11 and 2015-16, the assessment of forces' financial sustainability found.