The Group's leaders continued to protest what they saw as a gradual abolition of intra-Party democracy throughout the early 1920s and joined Leon Trotsky's Left Opposition in 1923. In 1926 Sapronov and Smirnov formed the "Group of 15", which joined the United Opposition headed by Trotsky, Grigory Zinoviev and Lev Kamenev. They were expelled from the Communist Party at the 15th Party Congress in December 1927 along with the rest of the United Opposition.