In an interview Marina Litvinenko said: “I can say people are naive.
“But sometimes I hope there’s nothing behind this, because I don’t like to blame people of being corrupted or doing this because of money – which is very common in Russian politics.
“When he doesn’t believe it might happen in Russia, I just try to understand what has motivated him. His feeling – he loves Russia?
“Or because somebody has asked him to do this? Really difficult, for me, to blame him.”
Asked by Kay Burley on Sky News if she thought Mr Corbyn was naive, she answered: “It’s very strange to say about a politician for a long time in politics to be naive.”
Mr Corbyn has faced sustained criticism, including from his own MPs, over his failure to condemn the Kremlin directly for carrying out the Salisbury poisonings.
A former officer with the FSB secret service, Litvinenko fled to Britain in 2000 where he became a fierce critic of the Kremlin.
The 43-year-old died after radioactive polonium-210 was slipped into his tea in 2006, leading to a cooling of relations between London and Moscow.
A public inquiry into his killing concluded that President Putin probably approved his assassination.