The request announced today comes after a ruling last month that sensitive evidence, including documents relating to Russia's alleged role in the former agent turned Kremlin critic's death, must be excluded from the existing inquest on national security grounds.
Litvinenko's widow believes a separate inquiry will clarify what happened to Litvinenko, who died in 2006 after drinking tea laced with the radioactive isotope polonium-210 at a London hotel.
Coroner Robert Owen made the request to Justice Secretary Christopher Grayling.