Shlosberg is of Ashkenazi Jewish descent. He joined Yabloko in 1994, becoming head of the Pskov branch of the party in 1996. From 2011 to 2015 he was a member of the Pskov Oblast Assembly of Deputies.
He has gained fame in August 2014 when he made a publication for the newspaper «Pskovskaya guberniya», where he spread information about the suspicious deaths of troops of 76th Guards Air Assault Division, Leonid Kichatkin and Alexander Osipov.[4] Shlosberg claimed they died fighting in the Donbass.
In 2015, Shlosberg was deprived of authority by a court and by vote of fellow deputies. Shlosberg claims this was politically motivated.[5][6] That year, he ran for the post of chairman of the democratic party Yabloko. He was defeated by Emilia Slabunova in the second round.[7]
On 4 July 2016 he announced he was running for Parliament, in that year's State Duma Election, but lost the election in his constituency, coming in fifth with around 6% of the vote.[8][9] Nonetheless, that same election, Yabloko won one seat in the Pskov Oblast Assembly of Deputies, and Shlosberg returned to the legislature.[10][11]
In 2021, Shlosberg decided to run in the 2021 State Duma Elections, again as a candidate of Yabloko. However this time he is running in the Khovrino constituency in Moscow, instead of his home district of Pskov.[12]
He also ran in the simultaneous Pskov Oblast Assembly elections. On 3 August 2021 his registration as a candidate was declined, due to alleged links with banned Anti-Corruption Foundation. However, on the next day he was registered, due to the fact that the court decision to ban Anti-Corruption Foundation was not yet final.
Regarding State Duma elections, however, on 9 August 2021 Moscow city court annulled his registration as a candidate, also due to alleged links with Anti-Corruption Foundation. Then he was also excluded from the federal Yabloko party list.[13]
In April 2022, following the increased repression after the 2022 Russian invasion of Ukraine, Russian police filed charges against him and his wife for having "discredited" the Russian military.[14]
