While this some data is already held on a voluntary basis, the government is discussing plans for an email database, which would give the police access to email and search information about users.
"I'm afraid we just don't trust any government or any organisation to keep that much very sensitive information about us all and to keep it safe," Shami Chakrabarti, director of human rights organisation Liberty, told BBC News.
David Banisar, deputy director of human rights group Privacy International, has written extensively on these issues, recently looking at the protection of journalists' sources and the impact of European terrorism laws on media.
"It [the proposed database] gives the police power to access information, but very little oversight as to what they can do with it," he says.
Banisar's concern is that everyone's data will be collected, whether or not they are under investigation.
"This is part of an international trend on data collection and we're seeing cases already where information is being abused by the [UK] police," he says, referring to regional newspaper journalists Sally Murrer, who faced a prison sentence for receiving leaked police information until the case was overturned in the High Court; and Mark Bulstrode, whose mobile phone records were seized by the police.
But the database itself is not the only issue: "There aren't any rules and that's the problem," says Banisar.
The law allows collection of information about emails and internet search, a sign of 'broad powers without any limitations', he adds.
Threat to journalism
"The database itself will have a chilling effect. If you're a journalist you're going to have to go through some extraordinary measures if you believe the police are going to be interested in who you're talking to," explains Banisar.
""For example, in other countries, journalists have to leave cell phones at home when they go to meet sources, they have to set up these ridiculous procedures where they leave plants on porches or send anonymous letters (...) or something to be able to reach the source."
This approach is not normally taken by British journalists, particularly at a regional level, or non-investigative journalists, he adds.
"But this [the database] gives the police the ability to turn anything into major case," he says, unlike the warrant system where the police 'has to prove to someone there's a reasonable investigation going on'.
"[It's] treating the whole public like we're all criminals, on the off-hand chance that at some part in the future we might actually be suspected of something."
UK pushed legislation through
Banisar, like other critics of the plans, believes the UK pushed this legislation through by 'policy-laundering'.
"The UK here is frankly jumping ahead because they were the people pushing it in the first place.
"This is one of those things where the UK government wanted something, so they went to the EU to get them to adopt it, so they could go back to the public and say 'we have to do this'."
Not too late to block
Human rights organisations could stand against such a database, Banisar says, citing cases in Ireland and Germany fighting the collection of digital information.
In the US there is such opposition to digital information collection that he can't foresee a similar plan ever being implemented in the country.
"It's fundamentally undemocratic. The first country which implemented this mass collection of data was Saudi Arabia. This is something as a long-standing democracy we shouldn't accept."
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