Boris Johnson has said police funding is being "spaffed up the wall" by investigating historic child sex abuse cases.
In a radio interview, the former London Mayor said an "awful lot of money" was being spent on looking into old offences.
His comments came after he was asked whether cuts to police funding had contributed to problems on London's streets.
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"I think an awful lot of the money, an awful lot of police time, now goes into these historic offences and all this malarkey," he said.
"£60 million I saw was being spaffed up the wall on some investigation into historic child abuse and all this kind of thing."
Mr Johnson added that he supported an increased use of the stop-and-search tactic in an effort to crack down on knife crime in the capital.
"Keeping numbers high on the streets is certainly important. But the question is where you spend the money and where you deploy the officers," he added.