Image caption Civil liberties campaigners describe the proposals as a "snooper's charter"

Members of the public have a final chance to have their say on plans to store all their web browsing and social media data for 12 months.

The controversial plan - dubbed a "snooper's charter" by critics - is meant to aid the fight against crime.

But a Lib Dem MP on the committee scrutinising it has threatened to veto it unless privacy is safeguarded.

The consultation ends on Thursday with the government expected to push ahead with legislation later this year.

Ministers took the unusual step of publishing a bill in draft form so that interested parties could have their say on it - in recognition of its controversial nature.

A parliamentary committee began an inquiry into the draft Communications Data Bill in July, inviting organisations and individuals to submit written evidence by 23 August.

The proposed legislation would require internet service providers to store details of internet use in the UK for a year to allow police, intelligence services and tax inspectors to search it in the course of their investigations.

I think the parliamentarians are doing their best but they have been given an impossible job Jim Killock, Open Rights Group

Records will include people's activity on social network sites, webmail, internet phone calls and online gaming, though officers will still need a warrant to see the content of messages.

The inquiry by a cross-party committee of six MPs and six peers is asking whether the government has made clear what it hopes to achieve, and whether ministers have made a convincing case for the new powers.

The consultation is also examining whether the technology exists to enable reliable storage of data, and if proposals for parliamentary oversight are adequate.

The inquiry has heard oral evidence from representatives of the Home Office, the police, civil liberties groups and academics.

'Technical changes'

Ministers argue that changes are needed to ensure that law-enforcement agencies can access data about communication using new technology just as they are currently able to with older forms of communication.

They believe it is necessary to extend the retention of data to emails and internet traffic in order to combat serious crime, including terrorism.

Home Office security and counter-terrorism head Charles Farr told the committee that existing provisions had been "overtaken by technical changes in the communications industry and in the way people use communication, with the result that the data that public authorities have had access to in the past is no longer as readily available to them as it used to be".

Jim Killock of the Open Rights Group, who also gave evidence to the committee, described the inquiry as "extremely important from a democratic point of view… but in wider terms it isn't adequate".

Data Communications Bill The Bill extends the range of data telecoms firms will have to store for up to 12 months

It will include for the first time details of messages sent on social media, webmail, voice calls over the internet and gaming in addition to emails and phone calls

The data includes the time, duration, originator and recipient of a communication and the location of the device from which it is made

It does not include the content of messages - what is being said. Officers will need a warrant to see that

But they will not need the permission of a judge to see details of the time and place of messages provided they are investigating a crime or protecting national security

Four bodies will have access to data: Police, the Serious and Organised Crime Agency, the intelligence agencies and HM Revenue and Customs

Local authorities will face restrictions on the kinds of data they will be able to access

He said the Home Office had so far failed to provide details of how they will collect data and precisely what data would be collected.

"I think the parliamentarians are doing their best but they have been given an impossible job. They are having to guess at what the scheme might be."

Civil liberties

This view is echoed by Lib Dem MP Julian Huppert, a member of the committee, who says: "So far the Home Office has not made a well-argued case."

He said he could only support a bill in Parliament if it was substantially rewritten to address "massive incursions into civil liberties".

The previous Labour government was forced to scrap plans for a single database of telecoms records in 2009 after a public outcry and criticism from opposition parties.

The coalition agreement between the Conservatives and Lib Dems committed them to "implement a full programme of measures to reverse the substantial erosion of civil liberties and roll back state intrusion".

Mr Huppert said: "The challenge is to persuade the Home Office to stick to the coalition agreement."

The committee will hold more oral evidence sessions when Parliament returns from its summer break before reporting in November.