Mr Livingstone later offered an olive branch to Mr Johnson by closing an attack website aimed at the Mayor as he warned the election race was getting "out of hand". He said:
"Those of us who are leading candidates in this election have a duty to the electorate to rein it in and direct it to the issues at stake for Londoners.
"I suggest to Boris Johnson therefore that he and I work together to raise the tone and spirit of this election."
More top news
Striking rail workers and engineering works are set to cause a headache for many Britons travelling over the bank holiday weekend.
An eight-year-old boy has been caught on camera going for a joyride with two other young children in the car.
The law should be changed to allow assisted dying, the country's former top lawyer has said.