The Roskomnadzor media regulator is trying to block the app, saying the move is justified by the firm's refusal to hand over encryption keys that are needed to scramble messages.
However, Telegram's lawyer, Pavel Chikov, has hit back at the Russian governmeny, insisting that its argument is "groundless".
He explained in a statement: "The FSB's requirements to provide access to private conversations of users are unconstitutional, baseless, which cannot be fulfilled technically and legally."
The Dubai-based firm was given a deadline of April 4 to hand over the keys.
The drama comes shortly after the campaign group Privacy International warned internet users that their privacy concerns extend beyond Facebook.
The iconic social networking site has recently come under fire after it was revealed that the data of millions of Facebook users has been harvested, but the group has insisted that is just the "tip of the iceberg".
A spokeswoman recently told the BBC: "The current focus is on protecting your data being exploited by third parties, but your data is being exploited all the time.
"Many apps on your phone will have permission to access location data, your entire phone book and so on. It is just the tip of the iceberg."