The novel, Breakfast With Polonium, uses the bare bones of what is known about the murder of Litvinenko in November to weave a fictional tale of jealous love, a scheming President Vladimir Putin, and a vortex of murder and violence in London.

Exploiting the fact that there are more questions than answers about the case, a husband and wife team that specialises in penning thrillers based on true crimes, reasoned that the Russian public's curiosity about the murder will see the books fly off the shelves. The authors, Alexander and Natalya Pankov, put the book together in just over a month, easily outstripping British and Russian investigators who have yet to say who they believe killed Litvinenko by poisoning him with a massive dose of polonium-210 in London.

On his deathbed, Litvinenko blamed Mr Putin while Russia's largely state-controlled media suggested the murder was orchestrated by Boris Berezovsky, the UK-based billionaire oligarch who counted the poisoned man as a friend. Both deny any involvement in the killing. However Breakfast With Polonium suggests there was an old-fashioned motive: spurned love.

According to its authors, Litvinenko, who is renamed "Litovchenko" in the novel, was bumped off by the aide of an exiled oligarch living in London. In a colourful plot that has sadistic London-based Chechens and a dwarf former KGB agent, the writers have the murder being committed by an assistant to an oligarch called Ilya Borzovsky.

In the book, Litovchenko is killed as punishment for having an affair with Borzovsky's glamorous wife, something that the spurned and murderous aide wished he could be having.

Pankov said he saw nothing unethical about using the case as the backdrop for a work of fiction. "We don't write anything bad about [Litvinenko]," Pankov told The Moscow Times. "We don't offend anyone. We changed the name."

The murder has proved lucrative for publishers. The former BBC correspondent Martin Sixsmith has published the results of his own investigation while Litvinenko's widow, Marina, has put together a book on the mystery, as has The New York Times correspondent Alan Cowell.