Hearing ahead of full inquest also hears Litvinenko was working for MI6 when he was poisoned with polonium-210

The government's evidence relating to the death of Alexander Litvinenko amounts to a "prima facie case" that he was murdered by the Russian government, the coroner investigating his death has been told.

The former KGB officer was a paid MI6 agent at the time of his death in 2006, a pre-inquest hearing also heard, and was also working for the Spanish secret services supplying intelligence on Russian state involvement in organised crime.

Litvinenko died in a London hospital in November 2006, three weeks after drinking tea which had been poisoned with the radioactive isotope polonium-210.

The director of public prosecutions announced in May 2007 that it would seek to charge Andrei Lugovoi, a former KGB officer, with murder, prompting a diplomatic crisis between the UK and Russia, which refused a request for Lugovoi's extradition. Britain expelled four Russian diplomats, which was met by a tit-for-tat expulsion of four British embassy staff from Moscow. Lugovoi denies murder.

At a preliminary hearing on Thursday in advance of the full inquest into Litvinenko's death, Hugh Davies, counsel to the inquest, said an assessment of government documents "does establish a prima facie case as to the culpability of the Russian state in the death of Alexander Litvinenko".

Separately, a lawyer representing the dead man's widow, Marina, told the coroner, Sir Robert Owen, that Litvinenko had been "a paid agent and employee of MI6" at the time of his death, who was also, at the instigation of British intelligence, working for the Spanish secret service.

"The information that he was involved [in] providing to the Spanish ... involved organised crime, that's the Russian mafia activities in Spain and more widely," Ben Emmerson QC told the hearing.

Emmerson said the inquest would hear evidence that the murdered man had a dedicated MI6 handler who used the pseudonym Martin.

While he was dying in hospital, Emmerson said, Litvinenko had given Martin's number to a Metropolitan police officer and, without disclosing his MI6 connection, suggested the police follow up the connection. He said Litvinenko had also had a dedicated phone that he used only for phoning Martin.

"Martin will no doubt be a witness in this inquiry, once his identity has been made known to you," Emmerson told the coroner.

The inquest would also hear evidence that Lugovoi had been working with Litvinenko in supplying intelligence to Spain, the lawyer said, adding that the murdered man had also had a separate phone used only for his contact with the other Russian.

While he was dying in hospital, Litvinenko had phoned Lugovoi on this phone to tell him he was unwell and would be unable to join him on a planned trip to Spain, Emmerson said. The purpose of the trip was for both men to deliver intelligence about Russian mafia links to the Kremlin and Vladimir Putin.

So advanced were the arrangements for the trip that the conversation "descended to the level of discussing hotels", Emmerson said.

The case against Lugovoi centres on a meeting he and another Russian, Dmitry Kovtun, had with Litvinenko at the Palm bar at the Millennium hotel in Mayfair on 1 November 2006. It is alleged that Litvinenko's tea was poisoned with the polonium-210 at that meeting. Kovtun also denies involvement.

At the instigation of MI6, Emmerson said, Litvinenko had been supplying information to a Spanish prosecutor, José Grinda González, under the supervision of a separate Spanish handler who used the pseudonym Uri.

Emmerson cited a US embassy cable published in the 2010 Wikileaks disclosures that detailed a briefing given by Grinda González on 13 January 2010 to US officials in Madrid. At that meeting, the lawyer said, the prosecutor had quoted intelligence from Litvinenko that Russian security and intelligence services "control organised crime in Russia".

"Grinda stated that he believes this thesis is accurate," the lawyer quoted.

He said that payments from both the British and Spanish secret services had been deposited directly into the joint account Litvinenko shared with his wife.

Contrary to Davies's submission, Emmerson said the inquest should consider whether the British government had been culpable in failing to protect Litvinenko, arguing that "the very fact of a relationship between Mr Litvinenko and his employers MI6" placed a duty on the government to ensure his safety when asking him to undertake "dangerous operations".

"It's an inevitable inference from all of the evidence that prior to his death MI6 had carried out a detailed risk assessment and that risk assessment must in due course be disclosed."

Neil Garnham QC, counsel for the Home Office, representing MI6, said the government would not comment on claims that Litvinenko was a British agent. "It is central to Mrs Litvinenko's case that her husband was an employee of the British intelligence services. That is something about which I cannot or will not comment. I can neither confirm or deny it."

The Investigative Committee of the Russian Federation has indicated that it would like to be formally designated an "interested party" in the inquest, which would give it the right to make submissions to the coroner and appoint lawyers to cross examine witnesses.

Along with Marina Litvinenko, Luguvoi is represented at the inquiry as an interested party, as are the Home Office, the Metropolitan police and the Russian oligarch Boris Berezhovsky, a friend of Litvinenko who has successfully fought a libel action over allegations that he was involved in the murder.

The coroner will shortly rule on the scope of the inquest, including whether he will examine Russian or British state culpability, and whether he intends to sit with a jury.

Speaking outside Camden town hall after the hearing adjourned, Marina Litvinenko declined to comment on specific evidence raised in the hearing. She said: "I would like to say I appreciate already what was done today and I am looking forward to any decision that will be taken by the coroner."

The full inquest will open on 1 May 2013, the coroner said.

• This article was amended on 14 December 2012 to clarify that it was the Investigative Committee of the Russian Federation which indicated that it would like to be formally designated an "interested party" in the inquest. A misspelling of Neil Garnham's name was corrected and a superfluous "QC" removed after Hugh Davies' name.