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A human rights group is launching a crowd-funded legal challenge to the UK government's so-called "snoopers' charter".

Campaign group Liberty says the powers, which are used by intelligence agencies to collect large volumes of data from electronic devices, amount to an "assault on our freedom".

The Investigatory Powers Act gained royal assent in November.

The government has said it will defend the act.

Powers covered by the act allow state agencies to control and alter electronic devices, read texts, online messages and emails and listen in on calls, regardless of a suspicion of criminal activity.

'Most extreme surveillance regime'

The act forces communications companies to retain data of the who, where and when, but not the content of people's phone calls, emails, texts and web browsing history.

But Liberty wants to challenge the lawfulness of these powers and is asking the public to fund a judicial review.

Liberty director Martha Spurrier said: "Last year, this government exploited fear and distraction to quietly create the most extreme surveillance regime of any democracy in history.

"Hundreds of thousands of people have since called for this act's repeal because they see it for what it is - an unprecedented, unjustified assault on our freedom."

In November 2016, a petition asking the government to repeal the act attracted more than 118,000 signatures.

Investigatory Powers Act

Replaces the Regulation of Investigatory Powers Act

The government says it gives police and the intelligence agencies the tools to keep people safe and addressing "ongoing capability gaps"

But critics have dubbed it a "snoopers' charter", raising civil liberties concerns

Among the measures is the requirement for communications companies - like broadband or mobile phone providers - to hold a year's worth of communications data

The act was first proposed by Prime Minister Theresa May when she was home secretary and was approved by the House of Lords on 19 November.

Bulk powers are among the most controversial in the legislation, but security services and the government argue that they play a crucial role in counter-terrorism efforts.

Last month, the government faced calls to amend the act after the European Court of Justice found the "general and indiscriminate" retention of communications data was illegal.

EU judges said communications data could only be retained if it was used to fight serious crime.

The BBC's legal correspondent Clive Coleman said the government has said it will vigorously defend the act, which it says protects both privacy and security, had faced unprecedented parliamentary scrutiny and enjoyed cross parliamentary support.

Correction 15 March 2017: This article has been amended to remove a reference to the Regulation of Investigatory Powers Act expiring at the end of 2016.