Speaking on Wednesday at a Prime Minister's Questions session, the leader of the opposition slammed Telegram, saying that it has been described as the "app of choice for extremists."

Starmer also said that, while tributes were being made to MP Sir David Amess, who was stabbed to death last Friday in Essex, in what Scotland Yard declared a terrorist incident possibly linked to Islamist extremism, the app's users could access "videos of murders and violent threats against politicians, the LGBT community, women and Jews."

He quoted an anti-racism advocacy group, saying Telegram had "facilitated a subculture that cheerleads for terrorists" and insisted "tough sanctions are clearly needed." He asked Prime Minister Boris Johnson why the directors of apps that are failing to clamp down on online extremism are not facing "criminal" penalties.

Telegram, however, has taken steps in the past to protect its users against terrorism. In December 2016 it announced that the app was routinely removing up to 70 Islamic State channels per month. In a joint operation conducted in late 2019 with Europol, the platform said it had purged 43,000 terrorist-related user accounts.

Starmer's remarks come after media reports emerged that Amess' suspected killer, Ali Harbi Ali, had been radicalised by extremist content online.

In the wake of the fatal stabbing, Deputy Prime Minister and Justice Secretary Dominic Raab said that there was "a case" for removing the right to anonymity, as internet users should not be able to "abuse their position on social media from a veil of anonymity."