Reductions in police numbers are inevitable, the president of the Association of Chief Police Officers (Acpo) has warned.
Sir Hugh Orde's concerns came as he prepared to give a speech to Acpo's annual conference.
The Home Office, as one of the government departments not protected by ringfencing, faces a 25% reduction in its annual budget following George Osborne's emergency Budget.
"We will lose people in my prediction over the next few years," Sir Hugh told the Today programme.
He rejected the suggestion that 28,000 police officers would lose their jobs in the coming years as "alarmist", but policing minister Nick Herbert told the same programme that "it's absolutely clear it's going to be very tough".
Both men sought to emphasise the need for improved efficiencies, mainly through greater cooperation between police forces.
"It also falls to us to point out that the consequence of approaching structural reform in an uncoordinated way is that we will see a variety of approaches across the country depending on many factors," Sir Hugh is expected to say later.
"Size may be one of them but others include funding issues across forces, police authority views and geography.
"I am confident that colleagues will work tirelessly to achieve savings by collaborating but remain of the view that there is more potential if this is centrally led in a more strategic way."
Equipment procurement and IT systems, currently carried out and run separately by individual forces, could be areas that police and the government look to in their bid to drive down costs.
"The priority has got to be to drive out costs wherever we can through more efficient working and greater collaboration," Mr Herbert added.