HOME Secretary Amber Rudd has told tech giants in Silicon Valley to stop using “unbreakable” encryption software which she claims only benefits terrorists.

However, her attacks on social media companies such as WhatsApp have been condemned by human rights campaigners.

Rudd flew to California this week to warn internet firms that the UK Government will bring in new laws to crack down on extremist content if the companies fail to take action.

She is to attend San Francisco’s inaugural Global Internet Forum to Counter Terrorism to press home the message.

Both Prime Minister Theresa May and Rudd have called for a stop to internet “safe spaces” where they say terrorists plot and spread hate.

Rudd said she is urging social media companies such as Google, WhatsApp and Facebook to “work with us” to take down extremist posts. “Of course it is just one thing to talk about it, but what we want to see is real action,” she said. “And this forum is going to be a platform for delivering just that.

“We believe the best way to get this material removed from the internet is to let them show us they are doing it.

“Of course we can do legislation, we may yet do legislation, but the most effective way of delivering this outcome that we all want is to have this forum which they can lead on.

“We’re asking them to take action, but we will make sure that they do it. We are not sitting back from this, this is just the start.”

However, advocacy group Liberty said an attack on encryption was an attack on basic human rights.

“End-to-end encryption, core to popular messengers such as Whats App and Signal, gives our online conversations the same level of privacy that we usually have in the offline world,” said Liberty director Martha Spurrier.

“It’s like having a private conversation in a room — only the people in the conversation can read the messages. WhatsApp, criminals, stalkers, or jealous partners can’t listen in —and neither can the state.

“But Rudd is demanding that we sacrifice our private lives in the name of tackling terrorism. Her attack is as ignorant as it is authoritarian.”

Spurrier said police and intelligence agencies already had a range of “intrusive” means – including hacking – to spy on the phones of terror suspects, regardless of whether they are using encrypted messengers.

“And as a human rights organisation, we at Liberty work with people who truly rely on encryption for their protection from criminals or from the abuses of state surveillance.

“For whistleblowers, activists, journalists, sources, lawyers and victims of abuse, encryption is a lifeline.”

She added that in some places a private conversation on WhatsApp could even be lifesaving, whether for LGBT people or those fighting state oppression.

“What example does our Government set for the rest of the world with its self-professed ‘world-leading’ attacks on privacy?” asked Spurrier.