The Mayor of London Boris Johnson said Britain's intelligence services should be allowed to monitor internet and phone data of anyone who poses a threat to Britain.
Johnson, a key ally of the Conservative prime minister -- once believed to be a potential contender for the prime minister's seat, said British authorities must be "absolutely determined to monitor" those who may pose a threat to Britain.
"If they are a threat to our society then I want them properly listened to," Johnson said in response to the Paris attacks, which left more than a dozen people dead after three days of coordinated and planned terrorists attacks last week.
He also said those who are unwilling to accept British values should "go away."
The Paris terrorist attacks in early January brought fresh calls for police and intelligence services in the U.K. to be given stronger powers to monitor Internet, phone, and email use.
The chief of Britain's domestic intelligence agency, colloquially known as MI5, warned of the technology-related change that is "affecting our ability to deal" with ongoing threats to the U.K. and wider Europe.
Director-General Andrew Parker, whose tenure as the spy agency's chief began just over a year ago, said in a speech at the agency's headquarters that the interception of communications -- which includes the listening of phone calls and reading contents of emails -- forms a "critical part" in the intelligence agencies' toolkit.
Parker warned that the "further reduction" of the agency's interception capabilities would "seriously harm our ability to investigate and disrupt such threats in the future."
It comes as the Conservative-led coalition appealed for the reinstatement of powers struck down weeks before by the European Court of Justice.
The decision to repeal the data retention laws across the EU's 28 member states, which allowed the British government to search and access the Internet and phone call records of every British resident for up to two years, was met with controversy across the British government.
Emergency legislation went into effect weeks later, allowing MI5 and its other sister intelligence agencies to access data held by private companies, including Internet and phone providers.
European agencies are equally seeking greater powers to prevent similar attacks from happening within the region.
A statement released by interior ministers representing just shy of half of the region's member states said they were "concerned at the increasingly frequent use of the Internet to fuel hatred and violence," and that they aimed to work with Internet providers to report and remove material associated with "extremism."
The European Parliament is said to take up the issue later this year.