Fears of a "significant institutional overuse" by police forces of powers to access communications data are to be investigated by a surveillance watchdog.
Police officers and members of law enforcement agencies, such as the National Crime Agency, may be neglecting their duty to consider the impact their actions have on an individual's privacy, the Interception of Communications Commissioner Sir Anthony May said.
Sir Anthony has decided to launch an inquiry into potential overuse after 514,608 requests for communications data were approved in 2013, which, despite being a 9% drop on the previous year, struck the commissioner as being a "very large number".
"It's an inquiry which starts from this raw figure - 514,608," Sir Anthony said. "The bulk of that figure is from criminal investigations in this jurisdiction and I have reckoned that's a large number and needs looking into, so I instructed the inspectors to do so."
Civil liberties campaigners called for the Government to urgently address the concerns raised in the report, while a Home Office spokesman said c ommunications data is a "crucial tool" in criminal investigations.
Communications data requests relate to the " who, when and where" of a communication but not the content and are made under part one, chapter two of the R egulation of Investigatory Powers Act (Ripa).
Out of 514,608 requests approved, 451,243 - or 87% - were made by police forces and law enforcement agencies, while 58,996 related to the intelligence services, 2,603 were made by other public authorities, such as Financial Conduct Authority, and 1,766 related to local authorities.
In his report, Sir Anthony says the total number "has the feel of being too many" and raises concerns police officers are turning to communications data as an "automatic resort".
The retired judge adds: "I have accordingly asked our inspectors to take a critical look at the constituents of this bulk to see if there might be a significant institutional overuse of the part one, chapter two powers.
"This may apply in particular to police forces and law enforcement agencies who between them account for approaching 90% of the bulk."
Sir Anthony went on: "Since a very large proportion of these communications data applications come from police and law enforcement investigations, it may be that criminal investigations generally are now conducted with such automatic resort to communications data that applications are made and justified as necessary and proportionate, when more emphasis is placed on advancing the investigations with the requirements of privacy unduly subordinated."
Emma Carr, deputy director of Big Brother Watch, said: "The Government needs to urgently address the fact that the Commissioner has grounds to believe some powers are institutionally over-used and that the records kept by public authorities are woefully inadequate.
"This does not require new legislation and should not wait until after the election.
"The fact that this report does not include the number of British citizens affected by these powers, or any meaningful detail on what sort of offences are being investigated is not good enough."
The use of interception warrants, which relate to the content of communications, fell to 2,760 in 2013 from 3,372 in the previous year.
Elsewhere in his annual report, the Commissioner slaps down claims made in the wake of the Edward Snowden disclosures that intelligence agencies have engaged in "random mass intrusion" into the lives of private, innocent citizens.
Sir Anthony said: "Public authorities do not misuse their powers... to engage in random mass intrusion into the private affairs of law abiding UK citizens. It would be comprehensively unlawful if they did."
He added that any member of the public who "does not associate with potential terrorists or serious criminals" can be assured that the interception agencies do not have "the slightest interest in examining their emails, their phone or postal communications or their use of the internet".
The Commissioner's comments come after Mr Snowden, a former contractor with America's National Security Agency (NSA), leaked confidential files to The Guardian, Washington Post, a location in Rio de Janeiro and another in Germany.
His disclosures revealed details of mass surveillance programmes such as the NSA-run Prism and the GCHQ-operated Tempora.
Under the £1 billion Tempora operation, Cheltenham-based GCHQ is understood to have secretly accessed fibre-optic cables carrying huge amounts of internet and communications data and shared the information with the NSA.
Home Secretary Theresa May said the report " makes clear that the intelligence agencies, law enforcement agencies and other public authorities operate lawfully, conscientiously and in the national interest".
"Importantly, the report finds that they do not engage in indiscriminate and random mass surveillance," she said. "Sir Anthony also concludes that the legislative framework for regulating and overseeing their activities is robust."
Mrs May went on: "The Government is committed to ensuring that law enforcement and intelligence agencies have the powers they need to investigate crime, protect the public and safeguard national security.
"That includes communications data which is vital in helping to keep the public safe: it is used to investigate crimes, bring offenders to justice and to save lives."
Foreign Secretary William Hague, in his role as minister responsible for GCHQ, said: " The intelligence agencies work tirelessly and with minimal recognition to keep us safe from terrorists, criminals, hostile governments and others who pose risks to our society. They exist to defend our freedoms and values, not to threaten them."
Publishing the report, Prime Minister David Cameron said in a written statement: "In light of concerns about the activities of the intelligence agencies, the quality of oversight, and a number of public concerns and myths that have developed in the light of media allegations linked to Edward Snowden, I believe his report provides an authoritative, expert and reassuring assessment of the lawfulness, necessity and proportionality of the intelligence agencies' work."