The use of calling cards to promote prostitution in Beijing hotels is an easy and lucrative way to reach clients, a woman engaged in so-called entertainment work was quoted as saying in a report by Beijing News on Monday.

"Pimping by cards costs less and earns a lot," the report quoted the woman as saying. "It is easy to do."

People involved in pimping distribute the cards, which typically advertise "services in different prices", to corridors or hotel rooms.

Even when such individuals are caught, punishment can be minimal.

An unnamed police officer told the News that it's hard to root out the use of calling cards for sexual services because distributors receive small administrative punishments, since no real prostitution is found.

The police said earlier this week that they had launched a crackdown on prostitution after a recent case in which a woman was attacked in the Yitel Hotel in the capital's Chaoyang district.

The woman, from Zhejiang province, posted a video of the attack last week showing her being dragged by a man.

The alleged attacker and four other suspects were detained on Saturday. Police said the attacker was part of a prostitution ring that used calling cards for pimping, and it is believed he mistook the woman for a competitor.

In September 2011, a similar crackdown in the city led to the seizure of more than 60,000 calling cards in one arrest, according to the news report.

Although people have to swipe room cards to use elevators in hotels like the one in the video, distributors of calling cards can take the stairs because doors on each floor are open, the report said.

"We sometimes see prostitution cards when we clean rooms," the report quoted a cleaner working for 7 Day Inn in Fengtai district as saying.

The cleaner added that the men distributing the cards try to avoid meeting staff members.