The Vatican wants to flash a red card at Germany over prostitution during the World Cup finals, lamenting that thousands of women risked being degraded to the point where they cost less than a ticket to a match.

Archishop Agostino Marchetto, the Vatican's top expert on migration, said the games risked permitting the violation of the human rights of many so-called sex workers and that German authorities had a duty to take action.

"Using soccer language, I think some red cards should be flashed at this industry, its clients and the authorities who are hosting the event," Marchetto told Vatican Radio.

With one million foreign visitors expected to flood into Germany from June 9, the likely sex industry boom has created demand for extra prostitutes who could come mainly from countries in Eastern Europe with major trafficking problems.

Sex workers in Germany, where prostitution is legal, can get health insurance, join a union and pay into a pension plan.

"Prostitution is a violation of the dignity of the human person, reducing (the person) to an object and instrument of sexual pleasure," said Marchetto, number two at the Pontifical Council for the Pastoral Care of Migrants.

"Women become merchandise to purchase, whose cost is less than a ticket to a soccer match," he said. Marchetto joined U.S. and European lawmakers who have urged German authorities to speak out against the increased trafficking of women likely to accompany the Cup finals.

Germany's brothel owners and pimps are expected to expand their operations and set up temporary "sex huts" and human rights advocates fear that thousands of women and children could be lured from poor countries and forced into prostitution to meet the huge sex trade demand.

"(It's bad enough) that prostitution is allowed ... but it is even worse that more than 40,000 women will enter the trade during the World Cup and many of them are forced to carry out this activity against their will, so they are objects of trafficking," Marchetto said.

"It is the responsibility, therefore, of German authorities," Marchetto said. "The ball is in their home pitch."