Russian online publications reported excerpts from Berezovsky's interview with BBC television (HardTalk show), accusing Kasparov of lying.
Kasparov denied that Berezovsky financed Another Russia, an opposition coalition comprising the United Civic Front.
"Boris Abramovich [Berezovsky] has said plenty, while Garry Kimovich [Kasparov] has repeatedly commented on his assertions. Right now Kasparov has many other, more pressing matters to attend to, and I do not think that he will comment on Berezovsky's latest remarks. We may issue an official reaction later, possibly a joint statement by all of Another Russia's leaders," said Denis Belunov, managing director of the United Civic Front, in an interview with RIA Novosti.
He said the UCF could sue Berezovsky, adding, however, that would have to be a coordinated decision.
But Berezovsky said he in fact refused to provide money to Kasparov when he asked for it three years ago in London, adding that the only reason he refused was because he understood that Kasparov is "weak," not tough enough to be the leader of that political movement.
Asked what his relationship with Another Russia is now, Berezovsky said that there is not one significant politician in Russia whom he has not financed.
He said this includes members of Another Russia, but declined to identify them.