Was Russian Dissident Poisoned by the State? Russian dissident Alexander Litvinenko was murdered in London in a "state-directed" execution, the former chief prosecutor who examined the case believes. Lord Macdonald QC was director of public prosecutions when Litvinenko died from the highly toxic poison polonium-210 in 2006 after meeting former KGB contacts in a London hotel. He told The Daily Telegraph he always had the "gravest suspicions" that the killing had involved "state actors" in Russia. A High Court judge, Sir Robert Owen, will on Thursday hold a preliminary hearing ahead of a full inquest into the highly controversial death. And Lord Macdonald called on the judge to ensure his investigation is as wide as possible to examine fully any possible links with Russia's hierarchy. That would include investigating claims the dissident was murdered because of his outspoken criticism of Russian President Vladimir Putin. It also emerged the two main suspects in the murder will have access to the details of investigations carried out by the police and security services in the U.K. Andrei Lugovoi, a former KGB bodyguard, and Dmitri Kovtun have been officially designated "interested parties" to the inquest, meaning they have access to any documents handed over. That will include a police report on the case, which is expected to only be provided in full to interested parties. In this image made available on November 25, 2006, Alexander Litvinenko is pictured at the Intensive Care Unit of University College Hospital on November 20, 2006 in London, England. The 43-year-old former KGB spy who died on Thursday 23rd November, accused Russian President Vladimir Putin in the involvement of his death. Mr Litvinenko died following the presence of the radioactive polonium-210 in his body. Russia's foreign intelligence service has denied any involvement in the case. Natasja Weitsz / Getty Images Both men remain in Russia and Lugovoi has resisted attempts to extradite him. He has since been elected to the Duma in Russia, giving him effective immunity from prosecution. He has denied any involvement in the incident and his lawyer has previously said even suicide should not be ruled out. It remains unknown whether the men will give evidence to the inquest, such as via a video link. Litvinenko, a former KGB agent, was allegedly poisoned with radioactive polonium in his tea during a meeting with former contacts at the Millennium Hotel in Grosvenor Square in November 2006. He died three weeks later in University College Hospital. Lawyers for his widow, Marina, have previously described the incident as "an act of nuclear terrorism on the streets of London." Lord Macdonald, who was DPP between 2003 and 2008, said: "From what I saw when I was DPP I had grave suspicions that there were state actors involved and that was why I called for a high court judge to conduct an inquest. If we have a case like this where there is the possibility of state actors involved it is good practice [to have a judge lead the inquest]. It is imperative that the inquest makes inquiries of that and looks at the possibility this was a directed action. It is going to be very important for public confidence that the inquest is as transparent as possible. Robert is expected to set a date for the full inquest in his preliminary session today. The hearing is also likely to discuss the nature and scope of evidence to be presented to the inquiry and how to handle any sensitive materials, especially from the security and intelligence services. The agencies would be concerned about any general intelligence being made public and will be legally represented during the hearings.