Russian Senator Vitaly Malkin resigned his seat in parliament over accusations that he also is an Israeli citizen.
A Russian law passed in 2006 prohibits lawmakers from holding dual citizenship.
Malkin denies the accusations, levied by opposition blogger Alexei Navalny, who posted documents online showing that Malkin, 60, maintained citizenship in Israel under the name of Avihur Ben Bar, according to the French news service AFP.
Malkin has said that he had Israeli citizenship but renounced it in 2007, shortly after the law was passed, according to Radio Free Europe.
Navalny also accused Malkin of holding undeclared property and business interests in Canada, also prohibited for lawmakers.