[2] He would remain at that post until November 1924 when he was moved to the Presidium of the Supreme Council of National Economy (VSNKh), the Soviet chief economic planning agency.

[2] On May 31, 1929, in Dearborn, Michigan, in his capacity as vice-chairman of VSNKh, Mezhlauk, together with President of Amtorg, Saul Bron, signed the agreement with the Ford Motor Company for assistance in building the first Soviet automobile plant (GAZ) near Nizhnii Novgorod (Gorky).

[2] He was also made vice-chairman of the Council of People's Commissars of the USSR and a full member of the Central Committee of the Communist Party of the Soviet Union.

When the Central Committee met in February 1937 to decide the fate of the former oppositionists Nikolai Bukharin and Alexei Rykov, Mezhlauk shouted at them: "You have been tormenting the party over many, many years and it is only thanks to the angelic patience of Comrade Stalin that we have not torn you politically to pieces for your vile terroristic work.

"[6] He also drew a cartoon showing the figures of Georgy Pyatakov and Lev Kamenev – who had both been shot – pointing at Bukharin and Rykov, depicted as wild animals.

Mezhlauk, who was half-Latvian and half-German, was arrested on December 1, 1937. and accused of treason, industrial sabotage, contacts with the German government, and heading a Latvian counter-revolutionary terrorist organization.

Younger brother, Martin Mezhlauk [ru] (1895–1918), was a Commissar of Jurisprudence in Kazan; he was killed by the White Army during the Russian Civil War.