Police leaders have a "responsibility" to highlight the impact of fresh budget cuts on the capacity to respond to a Paris-style terror attack, a senior officer has insisted.
On the eve of possible reductions in the Government's spending review, chair of the National Police Chiefs' Council (NPCC) Sara Thornton defended letters sent by senior officers to Home Secretary Theresa May last week.
One leaked note warned that a reduction in officer numbers would "severely impact" on their ability to respond to terrorism.
Opening the inaugural NPCC and Association of Police and Crime Commissioners (APCC) joint summit, Ms Thornton said the atrocity in the French capital has "brought the modern threat from terrorism into sharp focus".
The allocation of money to the police service is a matter for politicians, she said, but added: "As police chiefs, I think that we do have a responsibility to point out the operational impact of fewer officers and staff.
"Many of you are aware that letters were sent to the Home Secretary last week by several chiefs and it is no secret that we have been discussing firearms response, the role of neighbourhood policing in enabling intelligence flows, and the ability of the service to surge in times of crisis.
"We are accused of saying both too much and too little. Some say we wave the shroud, others that we are silent."
As well as terrorism, serious organised crime, modern slavery, cyber crime and fraud have presented new challenges for police over the last decade, she said.
"So this conference will have to come to grips with how the police service can respond to these profound changes," the former chief constable of Thames Valley police added.
"And we will be responding with less resource than we have now - we just don't know how much yet."
Ms Thornton sparked a storm of controversy earlier this year when she suggested burglary victims may not always be visited at home as forces shift their focus away from traditional offences in the wake of budget squeezes and staff cuts.
Addressing the conference in Manchester on Tuesday, she said: "Despite the hostile reception my comments have received in some quarters, I will repeat that efficiency savings alone will not provide the savings required if the government grant is reduced as proposed.
"Policing will be done differently and competing demands prioritised. It is important that we are candid and honest about that."
As an unprotected department, the Home Office, which provides the majority of the funding given to police forces in England and Wales, is facing cuts when Chancellor George Osborne sets out his spending plans for this parliament on Wednesday.
While not ruling out cuts to front line police numbers, Mr Osborne has said counter-terrorism funding will rise by 30% in the wake of the atrocity in the French capital and insisted he is "absolutely confident" security services would have sufficient resources to keep the population safe if Islamic State launched a gun and bomb attack in the UK.
Winston Roddick, PCC for North Wales and chairman of the APCC, said the terror threat level in the UK has stood at severe - the second highest level - for the last year.
He added: "Within this time there have been no specific adverse incidents in Britain and police services have been coping and coping well.
"However, the size and nature of future potential cuts puts this ability to cope at risk.
"If the threat level were to increase to critical - what then? This is why it is vitally important that we consider these issues."