The home secretary, Theresa May, had to endure heckling and jeering by rank and file police officers as she defended 20% funding cuts to policing and reforms to their pay and conditions.

May's 25-minute set-piece speech to the 1,200 strong Police Federation conference in Bournemouth ended in complete silence.

But she had to sit stony-faced through huge cheers and applause when one officer told her she was "a disgrace" and was no longer trusted by the police, and she was heckled when she promised not to privatise the police. "You already are," shouted one officer.

When May took to the stage at the Bournemouth conference centre she was greeted by a sea of banners saying "Enough is enough" and "20% cuts are criminal" held up by the audience of 1,200 officers. The home secretary had already taken pre-emptive steps to ensure she did not have to deliver her speech in front of a conference backdrop saying "20% cuts are criminal".

The home secretary insisted that the police funding cuts were "affordable and manageable" and directly answered accusations that policing had been singled out to take the pain. "Let's stop pretending the police are being picked on," she told them. "Every part of the public sector is having to take its share of the pain."

She also responded to growing voices within the Police Federation calling for them to be given the right to strike. "The right to strike is off the table. Keeping our communities safe is simply too important."

The home secretary strongly defended her reform programme and said whatever final conclusions came out of the Winsor review of their pay and conditions she promised the police would remain the best paid of the emergency services.

She also tried to allay concerns about the creeping privatisation of policing by promising that it would only be warranted police officers who made arrests, who led investigations and directed operations.

"We will not privatise patrolling," she said, but when she added: "It is because the police are crime-fighters that we will never privatise policing," one officer shouted: "You already are."

The home secretary had to sit through a 40-minute speech by Paul McKeever, the Police Federation chairman, who told her that 5,200 officers had already been lost, and that she was on the precipice of destroying a police service that was admired throughout the world.

"We are about to go through some fundamental change that will alter policing for ever," McKeever said.

"This is a bad deal for police officers, it's a bad deal for the service and most of all it's a bad deal for the British public."

During her speech, the home secretary announced that the police prosecution powers are to be extended to take over nearly 50% of the cases that go through magistrates' courts. She said they, rather than the Crown Prosecution Service, would have the power to prosecute 500,000 uncontested traffic cases where defendants either did not enter a plea or failed to turn up at court. She was considering extending police prosecutions to other low-level offences and would make an announcement later this summer, she said.