Trivial disputes between children are escalating to murder "within minutes" due to the influence of social media, Britain's top police officer has said.

Cressida Dick told The Times that the internet normalised violence, which is sped up by rivals goading each other on message boards.

It comes amid a recent spate of stabbings in London as 13 Londoners were killed in two weeks this month.

Met Commissioner Cressida Dick said websites and mobile phone applications such as YouTube, Snapchat and Instagram were partially to blame for the bloodshed.

"There's definitely something about the impact of social media in terms of people being able to go from slightly angry with each other to 'fight' very quickly," she said.

She said that insults or threats online "makes [violence] faster, it makes it harder for people to cool down. I'm sure it does rev people up".