Boris Johnson says checks should be made on the Russian banker who bid £160,000 for a tennis match involving the London Mayor and David Cameron.
Speaking to Sky News, Mr Johnson appeared to suggest the match might not go ahead if her husband - Russian ex-finance minister Vladimir Chernukhin - turned out to be "an intimate or a crony" of Mr Putin's.
"I think you have to do stuff that actually hits Putin and his government where it hurts," he said.
"I know about this tennis match they volunteered me for with some geezer. It is very important full checks are carried out to make sure this is not someone who is an intimate or a crony."
More top news
Weekend weather starts wet for some
Manchester United manager Louis van Gaal says Ryan Giggs will almost certainly succeed him at Old Trafford.
David Cameron has apologised for experiencing "brain fade" after he forgot which football team he supports.