More than 34,000 police jobs – one in six of the total – are expected to go as a result of a new round of deep public spending cuts after the general election, senior officers have warned.

Sir Hugh Orde, president of the Association of Chief Police Officers (Acpo), says official projections show that a further 20% cut in Home Office funding would inflict much greater damage on frontline policing than so far seen.

He also warns of serious implications for the statutory responsibilities of the police and for their role in safeguarding the most vulnerable in society.

Acpo’s estimate that 34,000 jobs out of a total police workforce of 205,000 could disappear within three years may yet prove to be too cautious.

The expectation that police will face a 20% cut in funding is based on grant reductions recommended by the police watchdog, Her Majesty’s Inspectorate of Constabulary (HMIC).

But senior Home Office officials have privately told the police in England and Wales that this will not be enough and they should expect and prepare for a deeper 25% cut in Whitehall funding after next May’s election.

Police and crime commissioners, from across the political spectrum, have warned the government that such savings will be impossible to deliver in many parts of England and Wales and that “forces are ready to fall over”.

Earlier this year HMIC identified 17 out of the 43 police forces that may “struggle to sustain themselves in the medium term in light of continued austerity”.

The 23% cut in police funding implemented as part of the austerity measures introduced in 2010 is expected to lead to the loss of 34,000 police officers and staff by March next year – and the same number of jobs could go in a new round of cuts.

The number of police officers has fallen from a peak of 141,600 at the time of the last election to 125,400 in March this year – a fall of 16,000 uniformed officers.

Ministers have already acknowledged that deeper real cuts in departmental budgets will be needed after the election, whichever party wins, because it is taking far longer than originally planned to pay off the deficit.

Cross-party protection for the health, schools and overseas aid budgets means that unprotected departments such as the Home Office and local government face particularly severe cuts.

“Modelling so far, based on HMIC recommendations for grant reduction, would suggest that if budgets were to be further reduced by 20% it is not unrealistic to expect forces to lose another 34,000 posts,” Orde has told Labour’s policing spokesman, Jack Dromey, in response to his request for an update on police resourcing.

Orde goes on: “This figure would rise exponentially if the cut imposed was to increase. The impact, however, in our view would be far greater on the frontline, which up to now forces have been trying to protect. A greater number of officer posts would be involved and this could potentially have serious implications for statutory responsibilities and the safeguarding of the most vulnerable.”

Orde said forces had drawn up plans for reductions involving 6,000 uniformed officers, 4,200 staff and 260 police community support officers between 2015 and 2017. “These are estimates and based on modelling to date. However, even after this modelling, large deficits remain meaning that further reductions are inevitable,” said Orde.

The home secretary, Theresa May, warned police forces in September that a further three years of spending reductions were likely after the election but made no mention of their scale.

She suggested that the integration of police, fire and ambulance emergency services and the widespread use of body-worn cameras and smartphone apps by police officers would be needed to save time and money.

Dromey said Acpo’s projection showed that at least one in six police officers would be cut from the line of duty.

“These will be the biggest cuts to any police service in Europe. In total, 34,000 officers and staff will have gone by early 2015. Acpo is predicting that at least a further 10,500 officers and staff will go by 2017,” said Dromey, adding that senior police officers were right to warn of the loss of 22,000 police officers.

He said a generation of progress in cutting crime was being reversed and that response times to 999 calls were now 30% longer.

“These will be the biggest cuts to any police service in Europe. Such savage cuts come at the worst possible time just when the demands on our police service mount by the day, from tackling child sex exploitation, thorough combating soaring fraud and online crime to the threats to our national security,” Dromey said.

Yvette Cooper, the shadow home secretary, pledged at the Labour conference to scrap the system of police and crime commissioners, which marks its second anniversary , and use the money to save 1,100 police jobs already planned to go next year.