Baroness Jowell has said social media companies "risk becoming agents of hate" in the wake of the Manchester attack.
The Labour former Cabinet minister said fake reports online meant "increasingly the social media companies have to be better citizens, better and more principled citizens, than they are being shown to be at the moment".
She told BBC Radio 4's Today programme: "This is, I think, something that has to be systematically discussed, engaged in, with the social media companies that they risk becoming agents of hate."
However, she said that "set against that" was "the humanity of the people of Manchester who have opened their homes, taken the trouble to provide care, interrupted their own lives so it's so important to remember that, in Manchester today, just as we saw in London, now more than 10 years ago".
She also called on the Government to provide a 10-year commitment to help those affected recover as well as "trained teams that can work and organise and deliver a sense of containment and certainty to these poor families".