Lebanon’s investigation of the deadly explosion that shook Beirut in August has suffered setbacks with political tensions building after the indictment of the country’s top sitting Sunni official. <a href="https://www.thenationalnews.com/world/mena/lebanese-prime-minister-and-three-former-ministers-charged-over-beirut-blast-1.1126267">Caretaker Prime Minister Hassan Diab, one of four senior politicians indicted last week </a>in connection to the August 4 blast that killed over 200 people, has refused to co-operate with the judge leading the investigation, arguing that the judicial order violated the law. On Monday, Judge Fadi Sawan rescheduled the questioning sessions for Mr Diab and three other former ministers who were charged with criminal negligence in connection to the blast, which involved the explosion of around 2,700 tonnes of ammonium nitrate that have been stockpiled at Beirut port for over six years. Judge Sawan set Mr Diab’s new questioning session for Friday morning while former Finance Minister Ali Hasan Khalil, and ex-ministers of Public Works and Transport Youssef Fenianos and Ghazi Zeaiter, have been summoned for questioning on Wednesday, Thursday and Friday respectively. Mr Zeaiter’s brother-in-law, Judge Ghassan Oweidat, stepped down on Monday from his role as prosecutor in the case, the National News Agency reported. The charges against Mr Diab fuelled long-simmering tensions between President Michel Aoun and Prime Minister-designate Saad Hariri, who labelled the indictment an “attack” on the post of prime minister, a position reserved for Sunnis under Lebanon's unwritten confessional power-sharing system. Hariri’s Future Movement said the investigation was being exploited to settle political scores and accused Mr Aoun of seeking to undermine the Taif Accord, the agreement that ended the country’s 15-year civil war. The accord introduced key amendments to the constitution, marking a shift in the power balance from the presidency, a post reserved for Christians, to the council of ministers. Following Mr Diab’s indictment, Mr Hariri spearheaded a campaign in solidarity with the caretaker PM. Mr Hariri was joined by Lebanon’s top Sunni religious leader, Mufti Abdul Latif Derian, and former prime ministers Najib Mikati and Fouad Siniora. Mr Mikati and Mr Siniora said the charges were politically driven and violated the constitution, which shield officials against prosecution for decisions made in their line of work. The recent charges, however, could set a precedent for judges to prosecute former and current ministers accused of wrongdoing, legal experts argue. The latest developments appeared to further complicate negotiations over the formation of a Cabinet before a visit by French President Emanuel Macron to Lebanon next week. On Monday, Mr Hariri accused the president and the Free Patriotic Movement of obstructing the Cabinet formation by demanding over a third of the seats and consequently the power to veto key government resolutions. Mr Macron has repeatedly called on the country’s political leaders to form a “credible” government that commits to fighting corruption in exchange for billions of dollars in financial aid from the international community. But his calls fell on deaf ears. After months of political bickering, Mr Hariri failed to secure the approval of the president on a cabinet line-up of non-partisan experts he proposed last week. The president retaliated with a counterproposal that brought negotiations back to square one, insisting that Mr Hariri consults with all political parties on the Cabinet make-up. Mr Aoun also denied interfering in the investigation into the blast, which forced the resignation of Mr Diab's government. The blast injured 6,000 people, displaced 300,000 families and caused an estimated 15 billion dollars in damages, further exacerbating Lebanon's economic woes. The World Bank has recently warned that over half of the country’s population will fall into poverty by 2021 if no reforms are undertaken.