A British Cabinet minister accused Russian President Vladimir Putin of "attacks on individual liberty and on democracy" and said Sunday that relations with Moscow were strained after a former KGB agent was poisoned to death in London.

Peter Hain, the government's Northern Ireland Secretary, said Putin's tenure had been clouded by incidents "including an extremely murky murder of the senior Russian journalist" Anna Politkovskaya.

They were the strongest comments leveled at Moscow since Alexander Litvinenko died Thursday from poisoning by the radioactive element polonium-210. In a dramatic statement dictated from his hospital bed and read outside the hospital after his death, the Kremlin critic accused the "barbaric and ruthless" Putin of ordering his poisoning.

"His success in binding what is a disintegrating nation together with an economy that was collapsing into Mafioso style chaos, his success in that must be balanced against the fact there have been huge attacks on individual liberty and on democracy," Hain said of Putin. "And it's important that he retakes the democratic road in my view," he told British Broadcasting Corp. He agreed when asked if relations with Moscow were at a "tricky stage."

British officials have so far avoided blaming Moscow for Litvinenko's death and Hain did not comment directly on the case.

But opposition leaders demanded Sunday that the government explain what it knows about the poisoning and, in particular, how the deadly nuclear material used to poison the 43-year-old Litvinenko found its way into Britain.

Litvinenko told police he believed he was poisoned Nov. 1 while investigating the October slaying of Politkovskaya, another critic of Putin's government. The ex-spy was moved to intensive care last week after his hair fell out, his throat became swollen, and his immune and nervous systems suffered severe damage.

London's Metropolitan Police said they were investigating a "suspicious death," rather than a murder. They have not ruled out the possibility that Litvinenko may have poisoned himself.

Litvinenko's friends and allies in London's Russian emigre community blamed Putin, who has denied any involvement and called the death a tragedy.

Russian officials could not be reached for comment Sunday on Hain's remarks.

Home Secretary John Reid, Britain's top law-and-order official, refused to speculate about who might have killed Litvinenko. "I don't think it's for me as a politician to be making judgments that a policeman should make," he told Scotland's Radio Clyde.

The main opposition Conservative Party demanded the government make a statement in the House of Commons on Monday outlining what it knew about the case and how polonium-210 — a rare radioactive element usually produced in a nuclear reactor or particle accelerator — got into Britain.

"It is essential that other dissidents living in Britain are reassured about their safety and there are also questions about how polonium-210 came to be used in Britain," said David Davis, the Conservative law-and-order spokesman.

Relations between Russia and Britain have remained cool since the end of the Cold War. London has infuriated Moscow by offering refuge to self-exiled tycoon Boris Berezovsky, a Kremlin critic wanted in Russia on money-laundering charges, and Akhmed Zakayev, a representative of late Chechen rebel chief Aslan Maskhadov.

In January, Russia's Federal Security Service, the FSB, accused four British diplomats of spying, showing on state-run television sophisticated communications equipment concealed in a fake rock, which it said the Britons hid in a Moscow park to use to contact Russian agents.

The ex-spy's death sparked a huge public health alert, with authorities preparing to test scores of people who may have come into contact with Litvinenko for traces of radiation.

"There is a lot of radioactivity involved," the Health Protection Agency's director of radiation, chemicals and environmental hazards, Roger Cox, told Sky News television.

But the agency insisted the risk to others was low because polonium-210 can only contaminate if it is ingested, inhaled or taken in through a wound.

Litvinenko's contaminated body was released to a coroner late Saturday, and government pathologists were awaiting advice on whether it was safe to perform an autopsy.

On Sunday, Alexander Lebedev, a former KGB spy who is a member of the Russian parliament, said Putin's government played no part in the death.

"I completely rule out the possibility of that being done on official orders from anyone in the authorities," Lebedev told Sky News.

The Sunday Times reported that as he lay dying, Litvinenko named an alleged Russian agent he feared had been sent to hunt him down. Litvinenko claimed the Russian agent was not directly involved in his poisoning but had been sent to monitor his activities, the newspaper said.

Police said they could not immediately confirm whether officers would seek to interview the alleged Russian agent. The Foreign Office said it has asked Moscow for help with the investigation.

Litvinenko worked for the KGB and its successor, the FSB. In 1998, he publicly accused his superiors of ordering him to kill Berezovsky and spent nine months in jail from 1999 on charges of abuse of office. He was later acquitted and in 2000 sought asylum in Britain.