London voters warned that Hell awaits them

In Dante's inferno, the ninth and innermost circle of hell is reserved for those who have committed vile acts of treachery against people who had reason to trust them, such as Cain, and Judas Iscariot.

And into that same terrifying pit of fire will be cast those London voters who commit the unforgivable act next May of not voting to return their former mayor, Ken Livingstone, back into the office he loves.

At least that is how things stand if you believe Livingstone. The 66-year-old is living up to his reputation for unpredictability and a love of attention by threatening eternal damnation on voters who fail to give him their vote in his forthcoming showdown with Boris Johnson.

He also suggested that the mayoral contest between him and Johnson will be the clearest choice between right and wrong since Winston Churchill took on the Third Reich.

"It's a simple choice between good and evil," Livingstone said.

"I don't think it's been so clear since the great struggle between Churchill and Hitler. 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'."

Although Livingstone was joking, his humour did not go down well on the Tory side. Officially, Johnson and his campaign team were ignoring the comments, but others described them as divisive and claimed that they proved that Livingstone is unfit for high office.

"Comparing rival politicians to Hitler is in incredibly poor taste," said Gavin Barwell, the Tory MP whose Croydon Central constituency was the scene of the worst of last week's rioting. "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 his standards. 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."

Livingstone was keen to emphasise his physical fitness for the mayoral contest, adding, in the interview with Total Politics magazine: "I've got a low cholesterol level. My doctor says I've got the same heart profile as an Olympic runner. I can't run like a champion athlete, but I can cope with a lot of stress ... [My teeth] are shit. That's the weakness."

Livingstone - like Johnson - is well known for pushing the boundaries of what an elected politician can get away with. When he was Mayor of London eight years ago, he was briefly barred from office for likening a reporter who had annoyed him to a Nazi camp guard and refusing to retract when the journalist identified himself as a Jew.

Livingstone is fighting his fourth mayoral contest. He was London's first directly elected mayor in 2000-08, but lost to Johnson during a low point in Labour's fortunes in 2008. He was also the last leader of the Greater London Council before it was abolished in 1986. His spokesman said: "Anyone reading the full quote will see Ken's comments were clearly made in a spirit of humour during a light-hearted interview."

A source close to 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."

Mr Livingstone's relations with most Labour leaders have been notoriously bad, but in this latest interview he said that he was on good terms with Ed Miliband.

"It's the first time since John Smith died [in 1994] that there's a Labour leader who actually likes me," he said. Independent