UK Home Secretary Amber Rudd has told Sky News messaging services like WhatsApp should give the security services access to their platforms in the fight against terror.
Her comments come after it emerged that Westminster attacker, Khalid Masood, sent an encrypted message via the application, minutes before his murderous assault.
Speaking to Sophy Ridge On Sunday, the Cabinet Minister also insisted social media companies must do more to deal with extremist material as part of the drive to combat terrorism.
Highlighting the "inadequate" efforts of tech firms to take down all terrorist content, Ms Rudd said they needed "to take responsibility for the fact that their platforms are being used by terrorists".
She is due to meet with internet giants Google, Twitter, and Facebook later this week to discuss the issue, and warned: "They're going to get a lot more than a ticking off."
Efforts of online companies to tackle terrorism "inadequate", says Home Secretary Amber Rudd #Ridge pic.twitter.com/LG8oHkQKtb
— SophyRidge On Sunday (@RidgeOnSunday) March 26, 2017
The Home Secretary did not rule out changing the law if needed, but said she would prefer the industry to take the lead.
She said: "I believe that they are more likely to have the answers. They're the ones who put together platforms and have the in-house expertise. They should be part of solution."
Ms Rudd also argued the use of encrypted messaging services by terrorists was "completely unacceptable".
She said: "I support end-to-end encryption; it has its role to play."
But she added: "We also need a system whereby when the police have an investigation, where the security services have put forward a warrant signed by the Home Secretary, we can get that information when a terrorist is involved.
"It is absurd to have a situation where terrorists are talking to each other on formal platform and it can't be accessed. I need to find a solution with them for that."
German-style laws "should be considered"
Chair of the Commons Home Affairs Select Committee Yvette Cooper said the Government should consider German-style laws to fine companies that fail to remove extreme material.
She said: "I think we're going to have to have much more pressure on them to act because I know that Amber Rudd wants to have another summit with them and another meeting with them. I'm sure that's very good.
"But David Cameron had lots and lots of meetings with them that kind of went around these issues again and again.
"I think they have to act."
Although not as well-known as Google, Twitter and Facebook, there are concerns that apps such as Telegram, Wordpress and Justpaste.it are being used by extremists to plot and publicise attacks.
