"This is outrageous. Our posters are being removed, across the country you could say, which is illegal, because we concluded all the necessary contracts and paid all the fees," the unnamed representative told Interfax.
Prokhorov's office plans to file a formal complaint with the Central Election Committee.
The candidate's representative said numerous banners had been taken down in several Russian cities, including seven of 21 in Saratov, all nine in Nizhny Novgorod, seven of 33 at St. Petersburg's Moskovsky Station, and 64 out of 77 at train stations in Moscow.
An unnamed source from the Volga division of Russian Railways told Interfax that the signs taken down near the Saratov train station had been removed over the course of routine work on a previously planned construction project.
Signs supporting Prokhorov were also taken down in 2011 during a campaign to raise the businessman's public profile after he became head of the Right Cause party. The party said at the time that around 300 signs had been removed, RIA-Novosti reported.