The police ministry does not manipulate crime statistics as they are calculated in line with international standards, Deputy Police Minister Maggie Sotyu said on Thursday.

"To create an impression that the police are manipulating the stats is not only downright irresponsible," she told Parliament, according to a statement from her office.

"It could also mean that distracters [sic] will never be happy when this ANC-led government is actually making good progress in providing safety to all South African inhabitants."

Crime researchers questioned the validity of statistics showing a decline in serious and violent crimes for 2011/12 when statistics were released in September.

There were declines in all seven categories of contact crime – murder, attempted murder, sexual offences, assault with intent to do grievous bodily harm, common assault, aggravated robbery and common robbery.

Sotyu said all figures were calculated as ratios per 100 000 of the population, in line with international practice.

"This is done to equalise our population growth and be able to scientifically compare provinces of different sizes with each other."

She said the police ministry delivered the statistics with "full cognisance" of the police's problems.

The police ministry took the Victims of Crime Survey (VOCS), published by Statistics South Africa, seriously in order to improve, she added.

"Any good democracy like ours does need good statistical data to identify and measure patterns and trends of criminal activities.

"But, statistical data is not the only measure for solving crime, because overemphasising the importance of crime statistics inevitably leads to politicising the interpretation of this data, resulting [in] narrow and dramatised questioning of the data."

The VOCS was conducted from January to December 2011. Sotyu said it endorsed the validity and credibility of crime statistics.

"VOCS 2011 will be a rich source of information to assist... in the planning of crime prevention as well as developing sharper policies and strategies."