Ken Livingstone sensationally compared The Evening Standard's coverage of his pledge to cut tube fares to a slur that Europe's Jews spread disease.
Speaking during a Student Union debate on Tuesday evening, the London mayoral candidate also claimed his Conservative rival had had a difficult childhood and accused bankers of having a cocaine habit.
Livingstone was quick to dismiss the "torrent of vile abuse" he had received from hostile media, singling out a recent "dishonest headline" that claimed "Ken Livingstone's fares cut damned by City".
"It is completely and utterly untrue", he said, "it ranks up there with the Mirror's 'Jews bring disease to Europe'."
The Labour candidate defended his previous comments where he labelled Boris Johnson a "lazy tosser". He told The Huffington Post UK during a question and answer session: "That was absolutely a serious analysis of his work-rate."
"You don't go through a childhood like that [his] without real long term and damaging consequences. It was an absolute nightmare what he went through - but we shouldn't have to pay for that now," he said. However, he did not elaborate on what difficulties he believed Johnson had faced.
"Part of the problem is that because he is incredibly intelligent, he always got through by cramming the night before. At Oxford, it was always a huge party - and then the night before, huge cramming and he sailed through it... He could always do that bit better."
Livingstone went on to criticise Johnson's campaigning style. He claimed that 50 organisations had tried to put together debates between the London mayoral candidates, and Johnson had agreed to only three. "He's very good at promoting himself, but not so good at the day-job" he said.
He attacked Johnson over high transport costs. The tube fares are the "highest in the world", he claimed, "the fares are used as a stealth tax". This came as part of Livingstone's major campaigning promise to cut fares - as part of his "Fare Deal".
The coalition was accused by Livingstone of pushing through policies "that Mrs Thatcher only had wet dreams about". He suggested that ministers struggled to resist the "fatal mistake that the banks could lead us to heaven".
"If you go into the City, you'll be on massive bonuses, and able to feed any amount of cocaine habit that you have" he said.
He was also positive on Labour's fortunes: "People are open to the fact that Labour might actually be right. The media are a bit scared that Ed Miliband might be real Labour".
Livingstone was keen to make clear how demanding it was to be Mayor of London: "Your job is to look for things you can do, to push the boundaries of your job description and to see how you can stretch those limitations in order to see how you can help people... but then I don't want to be Leader of the Tory party".
He claimed all Johnson cared about was his next job.
"You'll see his basic strategy is to bluster and bluff and push questions aside. He gets about half the questions done in those sessions [Mayor's Question Time] that I'd do," he said.
"For Boris, it is about being the next Tory party leader and being prime minister. Therefore, rather than doing the detailed nitty-gritty stuff of running London, which involves annoying people... what we've had is four years of photo-opportunities, prize-givings, ribbon cuttings and nice fluffy things - while ducking all the difficult issues."