Police, councils and the intelligence services made more than 500,000 requests to access private e-mails and telephone records in the UK last year, according to an annual surveillance report.
The figures, compiled by the Interception of Communications Commissioner, Paul Kennedy, found that about 1,500 surveillance requests were made every day in Britain.
That is the annual equivalent to one in every 78 people being targeted. It included 1,500 approved applications from local councils.
Each request allows public bodies to access data - which includes telephone records, e-mail and text message traffic - but not the actual content of conversations or messages.
"It doesn't allow you to see the content of the message or conversation. It's about the who, where and when - the time element essentially in directed surveillance," a Home Office spokesman said.
Although slightly down on last year, the total is up more than 40 per cent on two years ago.
The Liberal Democrats' home affairs spokesman Chris Huhne seized on the figures, saying they "beggared belief", warning that the UK appeared to have "sleepwalked into a surveillance state".
"Many of these operations carried out by the police and security services are necessary, but the sheer numbers are daunting," he said.
"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," Mr Huhne said.
"The government forgets that George Orwell's 1984 was a warning and not a blueprint," he said.
The Home Office responded by saying it was vital the right balance between individual privacy and collective security was struck when invoking the act.
"That is why the Home Office is clear these powers should only be used when they are proportionate," a spokesman said.
It said it had revised codes of practice relating to the act and on public bodies able to use techniques relating to it.
The Liberal Democrats say only a magistrate should be able to approve a request for surveillance, under the Regulation of Investigatory Powers Act (RIPA).
The act was introduced in 2000, to take account of technological change. It was extended in 2003 by the home secretary at the time, David Blunkett, to tackle serious crimes including terrorism.
In his report, Mr Kennedy also found 595 errors in interception requests last year, including mistakes made by the domestic and foreign intelligence agencies, MI5 and MI6.
The vast majority of requests to snoop on people's records were made by the police and security services.
But the report found that some were granted to council officials investigating trivial offences like dog fouling, fuelling concern that the act is being misused.