The Russian government has refused to take part in a public inquiry into the death of poisoned spy Alexander Litvinenko.
The investigative committee of the Russian Federation (ICRF), a law-enforcement agency that answers directly to President Vladimir Putin, has told inquiry chairman Sir Robert Owen it will not be a "core participant" in the process.
In a letter read to a directions hearing at the Royal Courts of Justice, the ICRF, sometimes dubbed the "Russian FBI", said it would not take part as it did not agree with powers granted in public inquiries that allow evidence to be held in closed session but still inform the findings.
Core participants are actively involved in the inquiry, can be represented by a barrister and can also seek to cross-examine witnesses and make opening and closing statements.
The move will be seen as a snub to the process as the ICRF had intended to take part in the inquest, which was taken over by the public inquiry, as "interested persons".
The session also heard arguments for and against broadcasting the inquiry live on the internet, as was done during the Leveson Inquiry into culture, practices and ethics of the press.
Sir Robert reserved making a decision to a later date. The chairman said the substantive hearings would start on January 27.
An additional preparatory hearing will be held on October 16.
Sir Robert formally opened the inquiry in July after Mr Litvinenko's widow Marina led a successful challenge against holding an inquest into his death.
Mr Litvinenko, who fled to Britain in 2000, died after drinking tea laced with radioactive polonium-210 while meeting two Russian men - one a former KGB officer, at the Millennium Hotel in London's Grosvenor Square.
His family believes he was working for MI6 at the time and was killed on the orders of the Kremlin.
Former KGB bodyguard Andrei Lugovoi and Dmitri Kovtun have been identified as the prime suspects in the killing, but both deny any involvement and remain in Russia.
Sir Robert previously said that alleged Russian state responsibility in the 43-year-old's death was of ''central importance to my investigation''.
However, Britain's responsibility for protecting the former KGB officer will not be investigated as part of the inquiry as there is no evidence to suggest any failings on the state's part.
Mrs Litvinenko fought for the probe into her husband's murder after Sir Robert said he could not hold a ''fair and fearless'' investigation as part of an inquest, and a public inquiry should take place instead.
The Government had previously resisted launching an inquiry, instead saying it would ''wait and see'' what a judge-led inquest found, but the High Court ruled the Home Secretary should reconsider the decision.
Although Mrs Litvinenko and her lawyers will not be able to see secret material, the chairman can take it into account, unlike in an inquest.