LONDON — The widow of a former Kremlin agent killed by radioactive poisoning plans to boycott an inquest unless the British government holds a public inquiry examining alleged Russian involvement in her husband's death, her lawyer said.

Lawyer Ben Emmerson told a pre-inquest hearing Tuesday that Marina Litvinenko "will consider herself unable to continue in the inquest process as an interested party" if the government refuses.

Alexander Litvinenko, an intelligence agent-turned-Kremlin critic, died in London in 2006 after drinking tea laced with the radioactive isotope polonium-210. Lawyers for his family say at the time of his death he was working for Britain's intelligence services, and that the Kremlin ordered his killing.

Britain accuses two Russians of the killing, but Moscow refuses to extradite them.

The British government has urged a coroner's inquest to withhold sensitive evidence relating to Russia's alleged role in Litvinenko's death and whether the killing could have been prevented, citing national security concerns.

In Britain, inquests are held — in public — to determine the facts whenever someone dies violently, unexpectedly or in disputed circumstances.

After months of legal wrangling, coroner Robert Owen said the secrecy restrictions meant that his inquest would be effectively powerless to determine what happened to Litvinenko.

Last week he said that a government-ordered inquiry — at which the secret evidence could be heard behind closed doors if need be — was now the best option for finding out the truth about the death.

Marina Litvinenko and a group of British media companies have backed his call for an inquiry. The government said it would consider the request.

Emmerson said the inquest process should be suspended until the government announces its decision.

"We are at a loss to see a good-faith reason to prevent a hearing which could get at the truth from going ahead," he said.

The hearing was adjourned to an unspecified date.