A total of 899 complaints were made against the force between 1 April last year and 31 March, compared to 991 in the same period the year before.
During the same period, the number of allegations included in these complaints decreased from 1573 to 1307, a fall of 17 per cent.
Between April last year and March, 84 allegations were substantiated following internal investigations, including 24 cases of "incivility", 20 of "irregularity of procedure", and 18 of "oppressive conduct or harassment".
In a report to the police board, Chief Constable David Strang said: "All police forces must ensure that any concerns raised by the public are dealt with professionally and efficiently.
"Any person who finds that a police force has not met their expectations, may make a complaint."
Complaints can now be made by any member of the public – even if not involved in an incident – and complaints can be made about officers not on duty.