MULTAN, Pakistan (REUTERS) - Pakistani businessman accused the country's ambassador to the United States on Thursday of blasphemy, a crime that carries the death penalty, in connection with a 2010 TV talk show, they said.

The accusation against Ambassador Sherry Rehman is the latest in a string of controversial blasphemy cases in Pakistan, a largely Muslim nation whose name translates as Land of the Pure.

According to Pakistan's blasphemy laws, anyone found to have uttered words derogatory to the Prophet Muhammad can be put to death. Those who are accused are sometimes lynched by mobs even before they reach court.

Ms Rehman has already faced death threats from militants after calling for reforms to the country's anti-blasphemy law, according to court documents. Two politicians who suggested reforming the law were assassinated.

The case against Ms Rehman was brought by businessman Muhammad Faheem Gill, 31, who said that the comments she made about the law on the Pakistani talk show in 2010 were blasphemous.

"I've been trying to get this case registered for the last three years, ever since I saw that TV show," Mr Gill told Reuters."I've even gone to the highest court. I'm glad that action will finally be taken now."

Mr Gill went to the Supreme Court with his complaint after police refused to register it. The court ordered police in the central Pakistani city of Multan to investigate.

Blasphemy accusations are on the rise, according to a report released by the Islamabad-based think tank, Center for Security Studies. At least 52 people accused of blasphemy have been killed since 1990.

The charge is difficult to defend since blasphemy is not defined and courts often hesitate to hear evidence, fearful that reproducing it will also be blasphemy.

Recent cases have included a teacher who made a mistake setting homework, a man who threw away a business card belonging to a man name Mohammed, and a Pakistani Christian girl, Rimsha Masih, who was accused of burning pages of Muslim holy texts last year.

The teenager was cleared by a court after it emerged that she may have been framed by a cleric trying to evict Christians from his area. She and her family are now in hiding.

Ms Rehman, a prominent member of the ruling Pakistan People's Party, was appointed as ambassador to the United States in November 2011.