Official crime figures are easily massaged under a Garda reporting system being rolled out across the force, rank-and-file leaders have claimed.
John Parker, president of the Garda Representative Association (GRA), said officers have been instructed over the past two years of new ways to classify offences.
Under the protocol, some crimes are being classed differently while others are going unrecorded because they are not backed up by statements, he said.
Mr Parker said anecdotal evidence showed officers who would have traditionally reported a burglary, for instance, may now class it as criminal damage because nothing was stolen during a break-in.
"Crime categorisation itself is a skill," he said.
"It is easy to massage statistics from one classification to another if all the boxes aren't ticked."
The GRA president, speaking ahead of the association's annual conference, said crimes are not recorded where a person makes a verbal complaint but not a full statement.
"Does that person not still deserve to be treated as crime victim?" he said.
"Yes, they do. For whatever reason they haven't followed through on the crime, it is still a crime, but it shouldn't be written off the books."
Mr Parker said Garda management have instructed officers that without a signed statement of complaint, then the alleged offence is not a crime.