Nationwide in 2006, the richest 10 percent of the Russian population earned 15 times more than the poorest 10 percent.
Russian Academy of Sciences economist Ruslan Grinberg warns that such a large gap could lead to social unrest.
Average monthly wages in Russia at the end of 2006 were around 9,000 rubles, or just over $300.
The state statistics service puts the official poverty level at 15 percent nationwide.
Kremlin economic advisor Arkady Dvorkovich has said the real level may be over 25 percent.