Turkey's foreign ministry summoned the German ambassador to Ankara on Sept. 27 to protest over comments made by a senior German politician who likened President Recep Tayyip Erdoğan to a "little sewer rat."
"We condemn in the strongest terms the insulting statements made by Wolfgang Kubicki, the vice-speaker of the German Federal Parliament, about our president (Erdoğan) in a speech during he Lower Saxony state election campaign," Turkish foreign ministry spokesman Tanju Bilgiç said in a statement.
"(Kubicki) is completely devoid of political morality and responsibility," Bilgiç said, adding that such "indecent statements essentially give an idea of Kubicki's political and moral level, and reveal his vulgarity."
Contacted by Reuters, Kubicki confirmed making the comment during an election campaign rally while trying to draw attention to a rise in the number of illegal migrants moving from Turkey along the so-called Balkan route towards Germany.
"A sewer rat is a small, cute, but at the same time clever and crafty creature that also appears in children's stories," Kubicki said, citing the popular animated movie "Ratatouille" as an example.
Kubicki, a lawmaker from the pro-business Free Democratic Party (FDP), one of the parties in Germany's ruling coalition, said Erdogan had made a good deal for Turkey when he agreed to curb the number of refugees entering the European Union in 2015.
"But at the same time we must note that the wave of refugees along the Balkan route (from Turkey) is again increasing, which is a challenge for German foreign and domestic policy," he said.
Turkey is a candidate for EU membership but negotiations have long been stalled amid disagreements on a number of issues including Ankara's human rights record, migration and geopolitics.
Insulting the president is a criminal offence in Turkey, where Erdoğan and his ruling Justice and Development Party (AKP) have held power for two decades.