MOSCOW — The sole suspect in the radiation poisoning death of a former KGB agent announced plans to run for Parliament yesterday on the ticket of a pro-Kremlin ultranationalist party.

Andrei Lugovoi, another former KGB officer who met with Alexander Litvinenko at a London hotel bar on November 1 hours before Litvinenko fell ill, told state-run Russia Today television that he had no desire to go into politics but changed his mind because of British accusations. Now a businessman who runs a private security agency, Mr. Lugovoi said yesterday that he would be no. 2 on the list of Vladimir Zhirinovsky’s Liberal Democratic Party in December’s parliamentary elections. Litvinenko, who became a vocal Kremlin critic and sought asylum in Britain, died November 23 in a London hospital after ingesting radioactive polonium-210. On his deathbed, he accused President Putin of being behind his poisoning — charges the Kremlin has fiercely denied.

Britain has identified Mr. Lugovoi as the main suspect in the death and demanded his extradition. Russia has rejected the demand, saying its constitution forbids it, and Mr. Putin has called the demands a vestige of British “colonial thinking.” Mr. Lugovoi has dismissed the accusations and accused British authorities of hurting his business interests.