The death of former KGB agent Alexander Litvinenko, who won asylum and citizenship in Britain and died in 2006 after drinking tea laced with the rare radioactive isotope polonium 210 while meeting with Russian contacts, chilled relations between Russia and Britain, The New York Times said Thursday.
The KGB is the former Soviet intelligence agency.
Lawyers in the regularly delayed preliminary hearing claimed British authorities were withholding evidence pertinent to Litvinenko's possible contacts with MI6, the British Secret Intelligence Service.
At the hearing Thursday, senior judge Sir Robert Own said, "It has been almost six years since his death. Such a delay is regrettable. There will be no further delay."
Hugh Davies, a lawyer representing the inquiry, said the British government requested references to MI6 in a London Metropolitan police report of Litvinenko's death be deleted, suggesting possible contact between the agency and the former spy be kept secret.
British prosecutors are seeking the extradition of Andrei Lugovoi, another former KGB. agent who was present at the meeting where Litvinenko was allegedly poisoned, to face murder charges. Lugovoi, now a member of the Russian Parliament, has declined to leave Russia, authorities saying the country's Constitution forbids such extradition of citizens, the newspaper said.