Labour has accused the coalition of overseeing a "shocking" 5,000 cut in police dealing with 999 emergencies.
Figures released under freedom of information laws suggest the number of "first responder" officers has dropped by 5,261 since the general election.
David Cameron has repeatedly insisted that frontline police have not been affected by cuts to budgets.
But shadow home secretary Yvette Cooper, who uncovered the latest details, said they showed that his claims were "bogus".
HM Inspectorate of Constabulary defines "first responders" as those responding to 999 calls, attending traffic accidents and being first at the scenes of crime and other incidents.
The forces that have apparently suffered the biggest culls include Devon and Cornwall, which had lost 540 "first responders" (25% of its total) between March 2010 and last December, and West Midlands, which lost 1,023 (19%).
The total figure is likely to be significantly higher, as only 23 of 43 forces have so far provided data.
Ms Cooper said: "This steep fall in the frontline teams who respond to 999 calls just goes to show how damaging it is for the Government to cut 16,000 police officers.
"We have consistently said the Government needs to change course and that frontline services are being hit by the 20% cut to police funding. The evidence is stacked against the Government and against their bogus claims about protecting frontline policing.
"Whether it is 'visible' or 'frontline' policing, however the Government want to phrase it, Theresa May and David Cameron's decision to cut 16,000 police officers is causing huge damage to police forces, and it is communities who will ultimately pay the price."
Police Minister Nick Herbert insisted the Government was protecting the frontline, insisting the debate was not all about the "raw numbers".
He accused Labour of "scaremongering", telling Sky News it was an "inconvenient truth" crime was falling despite reduced policy budgets.
Speaking to Dermot Murnaghan, he said: "I think it is shameful hypocrisy of Labour to be campaigning on this when they themselves would be reducing the number of officers.
"I really think it is appalling actually to suggest to people, and clearly Labour are scaremongering here, that somehow if you dial 999, you are not going to get the same response from police. Where is the evidence for that?"
He added: "What we are saying is that it is quite possible to reduce budgets, to look at again at how officers are deployed, to deal with the fact that there is this very large number in behind the scenes functions - that is actually too big a number - and make sure we are redeploying effectively and protecting the frontline service.
"My judgment is that is exactly what police forces are doing up and down the country. And we know that the proportion of the workforce on the frontline is actually increasing. We expect the visibility and availability of police officers, which is surely the key measure, to increase. We know that crime is continuing to come down."
Suggested For You
SUBSCRIBE AND FOLLOW
Get top stories and blog posts emailed to me each day. Newsletters may offer personalized content or advertisements.Learn more