A key adviser to President Recep Tayyip Erdoğan on Tuesday called for Turkey to embrace a presidential system to improve decision-making."The rapid change in the world is incapacitating the legal frame of parliamentarianism," Ihsan Şener told Anadolu Agency. "The executive should take quick and flexible decisions and this is possible with the presidency system."He said previous Turkish leaders had backed a presidential system to protect against political instability, citing former prime ministers such as Turgut Özal, Süleyman Demirel, Alparslan Türkeş and Necmettin Erbakan as proponents of a presidential model.Turkey has been a parliamentary democracy since the republic was founded in 1923. In recent months, President Erdoğan and the ruling Justice and Development (AK) Party have proposed switching to a presidential system.The office of president, which is traditionally a figurehead role free of party politics, was made subject to a popular vote for the first time in August 2014, when Erdoğan was elected. The post had previously been allocated by lawmakers in the Grand National Assembly.Şener, a former civil servant and AK Party deputy, added: "The direct election of the president by public legitimizes him and his policies. It removes governmental instability, which appears often in the parliamentary system."Turkey underwent two general elections last year as a June poll failed to produce a majority for any party. After coalition talks failed , a renewed vote held in November saw the AK Party returned to power.A parliamentary committee is currently looking into ways to reform the Turkish constitution, parts of which date back to military rule in the early 1980s. The administration has made constitutional change -- including a switch to a presidential model -- a key plank of its program.Although favoring constitutional reform, opposition parties are against a presidential system, fearing placing too much power in the hands of the presidency. The AK Party does not have a sufficient majority of deputies to make any changes on its own.