Spying powers used by police, intelligence agencies and other public authorities will be scrutinised by a newly-created watchdog from Friday.
Lord Justice Fulford was appointed as the UK’s first Investigatory Powers Commissioner in March.
The position was created as part of a strengthened oversight regime in the landmark Investigatory Powers Act, which passed into law last year.
The new law builds on changes to the Regulation of Investigatory Powers Act (RIPA) which were passed by Parliament in March 2015 after the Press Gazette Save Our Sources campaign.
Supported by the Investigatory Powers Commissioner’s Office (IPCO), Lord Justice Fulford will oversee the use of tactics such as bulk collection of communications data and interception of emails and phone calls.
The move brings the oversight regime under one umbrella, after it was previously split between three different bodies.
The IPCO will inspect hundreds of public authorities each year, including intelligence services, law enforcement agencies, local authorities and prisons.
A “double lock” regime will be introduced for the most intrusive techniques, so that warrants issued by a Secretary of State will now require the approval of a senior judge.
This measure will be brought into force incrementally over the next year and once it has started, judicial commissioners will consider whether they agree with ministers’ decisions to authorise the use of intrusive investigatory powers. Commissioners will have the power to refuse warrants.
Lord Justice Fulford said:”From today, and for the first time, investigatory powers will be overseen by a single body applying a consistent, rigorous and independent inspection regime across public authorities.
“This is an important milestone as we start to implement the new oversight powers set out in the Investigatory Powers Act.”
The Act was drawn up to bring a host of techniques used by security services, police and other authorities into one legal regime.
Home Secretary Amber Rudd said the Act offers a “world-leading oversight regime”.
She added: “In commencing his oversight responsibility, Lord Justice Fulford is playing a vital role in providing the enhanced safeguards we set out in the Act.”