"Ukraine, for example, if it ever joined the European Union, even though I don’t think anyone is really planning this, I don’t think it would improve its prosperity," Wagenknecht said in a documentary that was broadcast Sunday, on the Rossiya 1 television channel.
According to the official, the past experiences of admitting poorer countries into the eurozone led to polarization, as well as population decline.
"In Ukraine there is anything you could think of, but definitely not the social structure system where the interests of the majority are accounted for. There in my opinion, the interests of certain oligarchs play the [fundamental] role, who see an opportunity to get even richer by exports of agriculture and such things into the European Union," Wagenknecht explained.
Ukraine's relations with the European Union were a major trigger for February 2014 protests in the capital of Kiev that led to the overthrow of President Viktor Yanukovych.
The so-called Maidan demonstrations broke out soon after Yanukovych opted out of signing a Union Association Agreement with the European Union.
The new Ukrainian government signed and ratified the agreement last year, committing to adopt a wide range of economic, judicial and financial reforms, among others, under a deal with Brussels.
President of the European Parliament Martin Schulz said in July that it was "incredibly" difficult to say when Ukraine would be in a position to join the European Union, and recommended Kiev focus on current problems rather than its EU membership prospects.