Pakistan's Supreme Court has issued a contempt notice to Prime Minister Yousuf Raza Gilani for failing to follow the court's orders and open a corruption probe into the president.

The notice issued Monday orders the prime minister to appear before the court on January 19. If convicted of contempt of court, Mr. Gilani can be sent to jail and removed from his post.

The judges want the government to examine corruption allegations against President Asif Ali Zardari dating back to the 1990s. However, so far, Mr. Gilani has refused, saying Mr. Zardari enjoys immunity as the head of state.

The court order escalates the pressure on Pakistan's civilian government, which faces separate court battles and high tensions with the country's powerful military.

A Supreme Court-appointed panel is investigating the origins of an unsigned memo in which Pakistan's civilian government allegedly asked for U.S. help in reining in the Pakistani military, following the U.S. raid that killed Osama bin Laden last May.

The existence of the document came to light in October when Pakistani-American businessman Mansoor Ijaz accused the then-Pakistani ambassador to the United States, Husain Haqqani, of writing the memo. Haqqani denies he wrote the document and has since resigned.

U.S. military officials confirmed that the top U.S. military officer at the time, Admiral Mike Mullen, received the memo but did not find it credible.

Last week, Mr. Gilani accused army chief General Pervez Ashfaq Kayani and Inter-Services Intelligence head Lieutenant General Ahmad Shuja Pasha of acting unconstitutionally by making unilateral submissions to the ongoing inquiry.

In response, the military said his remarks will have “very serious ramifications,” and warned of “grievous consequences” for the country.