An overstretched and under-resourced police service has become reliant on officers' good will, according to a union representing the rank and file.
The Police Federation has warned that falling numbers and budget constraints have left the current policing model unsustainable and claims levels of overtime are having a detrimental impact on officers' lives.
Chairman Mark Lindsay said: "The PSNI is under-resourced and under-staffed.
"The consequence of this is that officers are working flat-out to keep the service ticking over. Indeed, over 90% said that even when they're off-duty, they're answering calls on police-related matters.
"This highlights the level to which policing in Northern Ireland has become reliant on the good will of officers."
The Federation's online "Goodwill Survey" was carried out over a three-month period and found that almost every respondent routinely works paid or unpaid overtime.
It found o n average, officers worked almost one day of unpaid overtime each month.
Six out of 10 had to rearrange childcare as a result of additional hours while overtime also forced eight out of 10 officers to cancel or miss an appointment.
Almost 90% missed a family or social event because they were working extra hours, the survey said.
According to the figures, two-fifths of officers worked most, if not all, of their daily rest breaks and a further fifth were unable to get eight hours of sleep as a direct result of working overtime more than 20 times in three months.
Mr Lindsay said: "Family life is severely disrupted. Plans are turned upside-down and this causes disappointment and upset and puts family relationships under severe strain.
"As an unwelcome consequence, there is a rise in long-term sickness levels. In turn, that places even more pressure on officers to plug gaping holes in the service.
"Reducing budgets and diminishing resources are the main causes for this degree of upheaval. All officers, from the constable to the chief constable, have undoubted commitment to effective policing, but there are limits to the service that can be provided under these conditions."
The union said political action was needed to address the issues highlighted.
"Ministers in the Executive must realise that service levels will deteriorate or fall short of what people have a right to expect if the budget continues to be attacked, and if the issues highlighted in this survey are not addressed as a matter of urgency. They need to carefully think what they are doing and what they want officers to deliver.
"We were operating with 700 fewer officers than we should have to meet a peacetime policing requirement. On top of this, we have 30 officers leaving every month and not being replaced, which should be a cause of great concern.
"The current policing model is unsustainable."