More than 2,000 complaints against gardaí were investigated by the Garda Síochána Ombudsman Commission last year, with more than a third relating to abuse of authority.
The Commission has released it's Annual Report for 2012, and it said that Gardaí frequently did not co-operate with requests for information, with delays of up to one and half years.
More than a third ( 34%) of complaints against gardaí related to abuse of authority, while 27% centred on neglect of duty.
Investigations led to 132 sanctions against gardaí, and convictions against four members of the force.
The Chair of the Commission Simon O'Brien said that during their investigations, gardaí often failed to respond to basic requests for information.
"We are at present unsatisfied with the issues of timeliness that are befalling us at this particular time," he said.
"In the time that we have been in operation that has only been acceded to in a small amount of occasion we often wait far too long for information and that can delay out investigations, obviously we all the knock on effect that has."