Labour's London mayoral candidate Ken Livingstone has been condemned for comparing his battle to regain City Hall from Boris Johnson to the "great struggle between Churchill and Hitler".
Aides insisted Mr Livingstone's comments, in which he said the contest next year was "a simple choice between good and evil" were light-hearted.
But they were seized on by political opponents, who said they showed Mr Livingstone was a "nasty, divisive character".
Mr Livingstone said: "It's a simple choice between good and evil - I don't think it's been so clear since the great struggle between Churchill and Hitler."
In comments, reported in Total Politics magazine, he added: "The people that don't vote for me will be weighed in the balance, come Judgment Day. The Archangel Gabriel will say 'You didn't vote for Ken Livingstone in 2012. Oh dear, burn forever. Your skin flayed for all eternity'."
Tory MP for Croydon Central Gavin Barwell said: "After the events of the last week, Londoners need a mayor who will unite our city, not one who regards people who don't share his views as evil.
"Comparing rival politicians to Hitler is in incredibly poor taste. And even to joke that Londoners who don't vote for him will 'burn forever' after everything we have been through in the past two weeks is crass even by Ken Livingstone's standards."
A source close to Mr Johnson said: "We always knew that Ken was a nasty, divisive character who would fight a dirty campaign but the Labour leader must surely distance himself from these, and similar comments, made in recent times and clarify to Londoners that this is not how his party conducts itself in 21st century democratic politics."
A spokesman for Mr Livingstone said: "Anyone reading the full quote will see Ken's comments were clearly made in a spirit of humour during a light-hearted interview.
"Tories may want to try to turn this into the central issue in the mayoral election to divert from the big issues, from rising unemployment to high fares and riots, but they are unlikely to succeed given the challenges facing London at present."