A judge leading the investigation into the massive Beirut port explosion last year has issued a subpoena for Lebanon's caretaker Prime Minister Hassan Diab, state media reported on Thursday.
Mr Diab, along with other ministers, has been charged with criminal negligence.
Judge Tarek Bitar rescheduled Mr Diab’s questioning for September 20 after the departing prime minister snubbed a summons to appear on Thursday before the judge, the National News Agency said.
One year after the blast, it remains unclear what triggered the explosion of hundreds of tonnes of ammonium nitrate, a highly explosive chemical that was stored illegally at Beirut port for more than six years with the knowledge of the government and security agencies.
Mr Diab was indicted along with three former ministers, who are also members of parliament, in connection with the blast that killed 214 people and injured thousands. All three have snubbed summons, arguing that the investigative judge had no authority to prosecute them under the constitution.
The latest subpoena drew criticism from three former prime ministers and premier-designate Najib Mikati.
Former premiers Saad Hariri, Fouad Siniora, Tamam Salam and prime minister-designate Najib Mikati issued a statement labeling the subpoena as an 'insult' and attack on the premiership, a post reserved for a Muslim Sunni under Lebanon's confessional power-sharing system.
The four politicians said the move was politicised and in violation of the law, suggesting the president, a Christian, was seeking to undermine the post of prime minister. They also called for the enactment of a law that lifts immunity on all top officials including the president.
Mr Bitar replaced Judge Fadi Sawan who was removed by the supreme court after indicting Mr Diab, along with former ministers Ali Hassan Khalil and Ghazi Zeaiter, both members of Speaker Nabih Berri’s parliamentary bloc.
Mr Bitar later also indicted MP and former Interior Minister Nohad Machnouk.
He asked Parliament for permission to question and prosecute the three MPs but his request was met with resistance. He was also denied permission by caretaker Interior Minister Mohamad Fehmi and the Higher Defence Council to question the heads of two security agencies.
The stalled investigation into the explosion has prompted protests by the families of victims who have accused government officials of trying to block the inquiry.
Mr Berri this month convened Parliament to vote on replacing the judicial inquiry into the blast with a parliamentary probe but the session lacked the necessary quorum as politicians came under attack from families of victims.
Mr Berri scheduled the session after a petition by a number of MPs requesting that the accused be tried before a special body that brings together politicians and senior judges.
Legal activists described the move as another attempt to derail the investigation.