The Litvinenko inquiry will "seriously complicate Russian-British ties", Russian Foreign Minister Sergei Lavrov said.
British government leaders could be sued for slander for their comments over the Litvinenko inquiry, Lavrov told a news conference.
The judge-led inquiry found President Vladimir Putin "probably" approved the assassination of former Russian spy Alexander Litvinenko in London.
Sir Robert Owen's report said Andrei Lugovoi and Dmitri Kovtun were probably acting under the direction of Moscow's FSB intelligence service when they poisoned him with radioactive polonium 210 at the Millennium Hotel in Mayfair in 2006.
He added he inquiry contained groundless accusations and left many questions unanswered.
Some of the key details of the Alexander Litvinenko case broken down into numbers.
Sir Robert Owen's report into the death of Alexander Litvinenko identified a number of reasons why he could have been killed.
Sir Robert Owen's report into the death of Alexander Litvinenko in London in 2006 was published on Thursday. Here are the key findings.