During this period, he also took part in the European Union group in the Uruguay Round multilateral trade negotiations.

From October 2002 to April 2004, he was Managing Director of the Hellenic Export Promotion Organisation (HEPO),[3][1] On 27 January 2015, Mardas was appointed as an independent member of the cabinet of Alexis Tsipras, taking the role of Alternate Minister of Revenue in the Ministry of Finance.

[4] In response, Sigmar Gabriel, the Vice Chancellor of Germany, called the claim "stupid".

[5] On 15 July 2015, before an important vote in the Greek parliament on a bailout package, Mardas condemned Panagiotis Lafazanis, the Minister of Productive Reconstruction, Environment and Energy, and the pro-Drachma elements of Syriza as "lost in space".

He was subsequently appointed as a Deputy Minister of Foreign Affairs, with responsibility for international economic relations.