Police, local councils and other UK public authorities made more than half-a-million requests to see citizens' communications data in 2008, according to a watchdog report.
The requests averaged out at about 1,500 a day, according to the report by interception of communications commissioner Sir Paul Kennedy.
On Monday, Liberal Democrat shadow home secretary Chris Huhne criticised the government for allowing that volume of communications data gathering.
"It cannot be a justified response to the problems we face in this country that the state is spying on half-a-million people a year," said Huhne in a statement. "We have sleepwalked into a surveillance state but without adequate safeguards. Having the home secretary in charge of authorisation is like asking the fox to guard the henhouse."
Under the Regulation of Investigatory Powers Act (Ripa), public authorities can ask service providers for data such as which individual has communicated with whom, and when and where this communication took place.
While the number of such requests decreased slightly last year compared with 2007, the Liberal Democrats said 2008 had seen an increase of 44 percent from 2006. Huhne added it was "baffling" that the state felt it necessary to collect data on such a high proportion of the population.
"The government forgets that George Orwell's 1984 was a warning, and not a blueprint," said Huhne. "We are still a long way from living under the Stasi, but it beggars belief that is necessary to spy on one in every 78 adults."
The use of communications data by local authorities has come under fire in the past. In December, the Home Office said it would launch a consultation, following revelations that local councils had used interception data to check for such offences as dog-fouling and whether people were putting their bins out on the wrong day.
The Home Office said on Monday that interception powers should be used only when they fit the circumstances.
"Of course it's vital that we strike the right balance between individual privacy and collective security, and that is why the Home Office is clear these powers should only be used when they are proportionate," it said in a statement "To ensure the appropriate use of Ripa, the Home Office has recently completed a public consultation on revised codes of practice, and on all public authorities able to use certain techniques relating to Ripa."
Kennedy said in his report that last year, 123 local authorities notified him of 1,553 requests for communications data. The commissioner relies on local authority notification of interception to compile figures. He and his team carried out only one inspection of a large local authority in 2008, and only eight inspections in total, due to "a temporary shortage of staff".
The number of complaints about unnecessary interception by the police and public authorities have increased by over 100 percent since 2007, Kennedy noted. The body which deals with interception complaints, the Investigatory Powers Tribunal, struggled with the additional workload.
"The inevitable result has been an increase in the time taken to deal with applications, given that there has been no increase in the size of the tribunal or in the size of its support staff," Kennedy added.