In summer 1917 was exiled by the French and Venizelists to Corsica from he returned after the end of WWI and the antivenizelist electoral win.
Mercouris was re-elected to parliament, in September 1932, and made vice-president of the People's Party which he left in November after a disagreement with its leader Panagis Tsaldaris.
He was among the more germanophilic adherents of the largely Italian fascism oriented authoritarian, corporatist, and anti-communist movement.
Prime Minister Ioannis Rallis (during the Axis occupation) appointed him Governor of the National Bank of Greece in 1943.
His brother Stamatis was later an MP for the United Democratic Left, and his niece was the famous actress, singer, and politician Melina Mercouri.