"The evaluation shows that the ban on the purchase of sexual services has had the intended effect and is an important instrument in preventing and combating prostitution and human trafficking for sexual purposes," the report said.
The report, which was handed to Justice Minister Beatrice Ask on Friday, maintained "that prostitution in Sweden, unlike in comparable countries, has not in any case increased since the introduction of the ban" on buying sexual services went into effect in 1999. It is not illegal to sell sexual services.
While the law punishing the client rather than the prostitute may not have caused a dramatic drop in prostitution as a whole, its true triumph, according to the report, is that "street prostitution in Sweden has been halved."
"This reduction may be considered to be a direct result of the criminalization of sex purchases," it said.
The drop in street prostitution has been a little less dramatic in Stockholm than in all of Sweden, but the capital nonetheless saw its number of streetwalkers drop from 280 in 1998 to 180 in 2008, according to official statistics quoted in the report.
Before Sweden became the first country in the world to criminalise buying sex, the number of street prostitutes in its capital was on a par with the number in the capitals of neighbouring Norway and Denmark.
But while the number of streetwalkers was slashed in Stockholm during the decade ending 2008, they had multiplied in Copenhagen and Oslo in the same period, the report said.
Norway introduced similar legislation to Sweden's on January 1, 2009.
The Swedish law stipulates that "purchasing a sexual service on one single occasion is sufficient for criminal liability," whether with money or other means such as alcohol or drugs.
But while cracking down on sex purchasers on the street has paid off, the report acknowledges that prostitution in other more hidden and obscure areas is hard to assess and limit.
The internet especially constitutes a new and dangerous arena, allowing sexual favours to be sold "in secret" and purchasers to remain "fairly invisible," it said.
"Prostitution where the initial contact is made over the internet is an important and growing arena," according to the report.
It stressed however that "the scale of this form of prostitution is more extensive in our neighbouring countries."
"There is nothing to indicate that a greater increase in prostitution over the internet has occurred in Sweden than in these comparable countries," it said, insisting that "this indicates that the ban has not led to street prostitution in Sweden shifting arenas to the internet."
Critics of the law claim it is driving prostitution into a dangerous shadowland where the mostly women selling sex are at a greater risk, but Friday's report insisted that was not the case.
The ban "is an important instrument to prevent and combat trafficking in human beings and to protect those people who are, or who risk becoming, involved in prostitution," it said
The report called on lawmakers to go even further and to double the sentence for sex purchasers from the maximum six months prison term today.
"In our view, the current level of penalties for certain sexual purchase offences is not proportionate to the seriousness of the crime," it said.
Swedish public radio reported on Friday that out of the 650 people who so far had been sentenced under the anti-prostitution law, none had been sent to prison.