Iranian President Hassan Rohani, already under pressure from conservatives for his tentative opening to the West, was criticised on Tuesday for what his opponents called a "lavish ball" thrown by the first lady.
Held in a palace of the deposed Mohammad Reza Shah in wealthy northern Tehran, the all-female dinner was held to mark Women's Day on Saturday which coincides with the birthday of the Prophet Mohammad's daughter Fatima, a paragon of Muslim virtue.
But hardliners in parliament said the event showed Rohani was indulging in luxury while normal Iranians suffer economic hardship, caused in part by Western economic sanctions.
"Can one preach austerity and financial sacrifice and yet throw a lavish party on the public coffers?" one of them said in parliament where at least eleven members signed a petition chastising the president.
Rohani's government is due to unveil price hikes on Thursday as part of a massive cutback in government subsidies for essential goods - a policy that will test his popular support 10 months after his surprise election win.
The president, who took Iran into talks with Western and other powers over the Islamic Republic's nuclear programme, rejected criticisms of the dinner.
"It is most shocking and regrettable that even a pure innocent gathering cannot escape an orchestrated chorus of gossip, slander and politically-motivated lies filling the air," his office said in a statement.
"All Islamic proscriptions were observed in this event ... women turned out in traditional folk dress ... only a few little girls capered and rejoiced," the statement added, to deflect impressions of a Western-style party, attended also by foreign guests and families of diplomats.
Rohani's wife, Sahebeh Arabi, has been slightly more visible than other first ladies in Iran and on some occasions had been photographed attending an educational or charity event, always clad in a long black chador.
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