Alex Beresford urged Mayor of London Sadiq Khan to "do more" to prevent knife crime amid the continuously rising epidemic in the city.
The Good Morning Britain weatherman lost his cousin Nathaniel Armstrong to knife crime earlier this year, just a week after his powerful call for change on the show.
On Wednesday, GMB hosts Piers Morgan and Susanna Reid spoke with Sadiq about what more could be done to prevent it, and what he was doing for this.
It's then that Susanna asked for Alex's thoughts on the topic, before he offered an insight into how he and his family have coped since the loss of Nathaniel.
The presenter, who hosted an ITV documentary on knife crime shortly after his loved one's murder, revealed there "were no words" for his loss.
Alex explained that the loss of someone to the crime "cuts deep inside" as he and his family try to move on.
Urging Sadiq to not just say more but "do more", he called the epidemic an "uphill struggle".
Alex said: "It feels like there does need to be more done, particularly in London, I feel like you could be more vocal on the issue of knife crime.
"It's not just about saying the right things, it's about doing the right things as well."
Alex said of his grief: "I mean words can't describe what it's like to lose one of your cousins to knife crime, and unfortunately Nathaniel isn't the only person I know who has lost their life to knife crime.
"It cuts you so deep inside, literally. Not a week goes by where I walk the streets of Britain where someone doesn't come up to me and say, 'I'm so sorry about what happened to your cousin, and I'm so glad you spoke out that day on Good Morning Britain'."
He added: "I wish it could change, this is an uphill struggle.
"It's not something we're gonna fix immediately, but people want an immediate fix."
Good Morning Britain airs weekdays at 6am on ITV.
