The Garda Ombudsman has received 957 complaints of malpractice against Gardaí this year.
They contain more than 1,400 separate allegations, which include sexual offences, theft and fraud.
Nearly 500 allegations are made against officers in Dublin, while there are also high numbers in Cork City, Kildare, Limerick and Galway.
The details have been released under the Freedom of Information Act.
Frank Thornton, vice-president of the Garda Representative Association, said the number of allegations is down on previous years.
"It's encouraging from a garda point of view because it shows the trend is declining," he said.
"If the trend continues to year-end the complaints against gardaí will be down 7% or 8% compared to last year, which also showed a drop compared to 2017."
Meanwhile, Sinn Féin's justice spokesman, Martin Kenny, claims the number of complaints is a concern.
He said: "The number of complaints I think is probably a reflection the problems people have out there.
"For very many people in the community when they deal An Garda Síochána it works out very well for them, but there is a lot of cases where it doesn't work out very well and they find that they have issues that they feel they were ineffective and didn't carry out the process of policing service that they expected."