A deepfake audio clip of the mayor was circulated on social media last week, in which an artificial voice purporting to be Mr Khan called for Armistice Day to be re-scheduled to make way for a pro-Palestinian march.
The Met Police said specialist officers reviewed the fake audio, but found that it "does not constitute a criminal offence".
An update on the matter was requested during Mayor’s Question Time at City Hall on Thursday by Tory assembly member Tony Devenish.
Mr Khan said: “It’s clear these videos were intended to sow seeds of hatred and division. I’d encourage anyone who comes across content like this to report it to the relevant social media platform to ensure it doesn’t get further traction with those who seek to divide us.”
Mr Devenish said he was surprised the video was not considered criminal, and that the London Assembly should write a cross-party letter to Met Commissioner Sir Mark Rowley about it.
“I think either the Met need to get better lawyers, or we need a change in law,” said Mr Devenish.
“I’m not sure which it is, but we need to make sure that we, unanimously round this table, do take this up, because we can’t have this kind of outrage.”
Lord Bailey - Mr Khan’s Conservative opponent in the 2021 mayoral election - asked the mayor directly: “Do you think that we need legislative change? Because I was quite stunned when the Met came back and said it’s not an illegal offence, considering the very high level of harm this could lead to.”
Mr Khan said he did not want to talk specifically about his own recent case, but that he had had conversations about it with the security minister, Tom Tugendhat MP.
He told Lord Bailey: “The Government is seized of the danger this poses. Just think about a future general election, think about - God forbid - future referenda…
“The Government does take it seriously, from the conversations I’ve had. It is a serious issue. Just think about the slippery slope, if we don’t take action.”
The mayor said London and the wider UK was well-placed to influence developments in AI for the better.
Lord Bailey replied: “I’m very worried about this. In the Black community, on our WhatsApp groups, there’s an awful lot of this stuff going around - and it’s leading to quite a lot of anger and hurt.”
The mayor agreed, pointing out that increasing numbers of people get their news from social media and that community tensions can be exploited through fake images and content.
He said: “People who want to cause damage [will] evolve and find new ways to cause us damage.
“You’re spot on. We’ve got to find new ways to respond to that and be pre-emptive, and that includes, by the way, social media companies.”