Bagus BT Saragih, Jakarta – For the first time since being established in 1998, the Prosperous Justice Party (PKS) celebrated its anniversary in a gloomy mood Sunday, with party leaders attempting to stave off possible demoralization among supporters.

In its previous 12 celebrations, party leaders could easily count off the list of achievements the Islamist party – the self-professed moral guardian of the nation – has attained. This time they had to defend themselves from embarrassing internal conflicts. A prominent PKS legislator was recently forced to quit from the House of Representatives after he was caught watching porn during a plenary session.

President Susilo Bambang Yudhoyono himself did not attend the party gathering. There was no explanation for his absence, but the President had issued strong signals that he was not satisfied with the party's behavior in the ruling coalition.

Presidential spokesman Julian Aldrin Pasha said the President had been with his family and close aides at Cipanas Palace since Saturday for "internal matters".

The PKS has four ministers in the Cabinet and is the only coalition partner not to have signed a new "political contract" with the President, a sign critics say indicated the President's reluctance to keep the PKS in the coalition.

"Be solid and enduring even though more obstacles and challenges are headed our way," party president Luthfi Hasan Ishaaq shouted Sunday before more than 250,000 PKS members and supporters who came from across the nation to the Gelora Bung Karno Stadium in Jakarta. "Keep working for Indonesia, God will make us strong."

Luthfi refrained from blaming specific people or parties for the PKS' recent woes. The party has been crippled by public criticism especially since one of its lawmakers, Arifinto, was captured by a photo-journalist watching a porn clip on his tablet computer during a plenary session at the House earlier this month.

Internet users lambasted the incident in droves, saying the PKS was one of the most aggressive supporters of the controversial 2008 Pornography Law. Controversial Communications and Information Minister Tifatul Sembiring, a PKS member, has repeatedly boasted of his "success" in blocking porn from the Internet in Indonesia.

A few weeks earlier, Anis Matta, a member of the party's national executive board and a House deputy speaker, was reported to the Corruption Eradication Commission (KPK) by party cofounder Yusuf Supendi for allegedly embezzling Rp 10 billion (US$1.15 million) in campaign funds. Yusuf threatened to air more of the party's dirty laundry. The PKS leadership described Yusuf's accusation as baseless.

Another PKS legislator, Mukhamad Misbakhun, is currently serving a two-year prison sentence following a high-profile corruption case. PKS leaders were publicly criticized for their reluctance to fire Misbakhun from the House despite his guilty verdict.

"Slanderous claims have been spread and traps [against us] have been set. This will continue until [the 2014 general elections]," Luthfi told the audience.

Despite a reputation of efficiently organizing its public meetings, Sunday's gathering caused hours of gridlock in key city streets around the Senayan sports complex. "The enthusiasm has caused traffic jams. We apologize for that," Triwisaksana, the chairman of the event's steering committee, said.

Party chief patron Hilmi Aminuddin suggested the audience "keep asking for God's help".

Of the six ruling coalition parties, only two sent their top leaders to attend the PKS' biggest event of the year: Democratic Party chairman Anas Urbaningrum and Golkar Party boss Aburizal Bakrie were both in attendance.

Although Luthfi has not signed the coalition's new agreement, the party's patron council decided on Saturday to approve it with a few reservations.

"We have some comments, questions and suggestions on the new agreement that we think the President should be made aware of," Luthfi told news portal tempointeraktif.com.

He said his party would send Yudhoyono a confidential letter containing the party's reaction to the agreement from the party's patron council meeting last week.