Some businesses which served police officers have been threatened in Co Derry.
The Police Federation, which represents rank and file officers, blamed misguided and small-minded individuals.
It is understood a statement was issued aimed at intimidating those who served members of the PSNI.
A Federation spokesman said: "The actions of some misguided and small-minded individuals are reprehensible and should stop immediately.
"They are shunned by the vast majority of people who want to get on with their lives.
"Officers are every bit a part of the community as are the local businesses on the receiving end of these threats."
He added: "Those behind the threats are a throwback to an era that thankfully is long since past.
"I would urge the community to ostracise those responsible and instead show their support for officers who are working to build a society free from this type of mindless behaviour."
Chief inspector Gordon McCalmont said police were public servants who kept the community safe and engaged daily with local businesses and people to do so.
"We also investigate reports of alleged criminality without fear or favour. We are committed to policing with the community."
Ross Hussey, Ulster Unionist Assembly member, said those behind the intimidation were cowards.
He added: "These threats are disgraceful and those responsible must be faced down and brought to book. This society has made its choice. It wants a police service and it wants normal policing.
"Those who would seek to threaten businesses who serve members of the PSNI are nothing more than bully boys and fascists with nothing to offer."
With the threat to police severe from dissident republicans, ministers at Stormont have been told they must agree more detail on tackling paramilitaries before £5 million from Westminster is released this year.
Mark Lindsay, Federation chairman, said: "The scourge of paramilitarism has got to be tackled, and tackled effectively. To do that, we need more officers on the ground."
He said there was a disconnect between the anti-paramilitary funding and the need to provide adequate resources to police.
"A pause by the Department of Justice in the salami-slicing of the PSNI budget would be a positive first step. We cannot afford to preside over the erosion of policing services simply to fulfil a balance sheet exercise," he added.
