"You can only expel him if there is concrete evidence that something has been going on. Unfortunately, police and intelligence apparently have no such proof", Hamacek told the national television.
The Respekt weekly reported in April that a Russian diplomat had brought ricin poison to Prague to murder Czech officials behind the dismantling of a Soviet war memorial. Czech TV disclosed the man's name, prompting calls for his expulsion and threats of violence.
The Russian embassy has condemned the accusations against the diplomat as "revolting and heinous" and demanded that he receive personal protection. Hamacek, who is also vice prime minister, said that Czech authorities were considering this request.