Image caption Ministers argue law enforcement agencies need to keep pace with changing technology

The Lib Dems are considering their support for government plans to give the police new powers to monitor email and internet use, the BBC has learned.

Party sources say leader Nick Clegg is ready to use a parliamentary report, due out next week, to oppose the plans.

The draft Communications Data Bill would allow police access to details of people's email and internet use, which many Lib Dems oppose.

But Home Office sources insist the bill would become law by 2014.

At the moment, the police and intelligence services can get access to information about people's mobile phone use.

The bill would extend those powers to cover email and the internet. The authorities would be able to see details of who communicated with whom, and when and where, but they would not be able to see the content of the message.

'Non-committal'

The Home Office says these powers are needed to help the police and intelligence services fight organised crime, terrorist networks and paedophile rings.

But critics argue they would infringe civil liberties and have branded the bill a "snoopers' charter".

Sources said Mr Clegg met the Prime Minister face to face earlier this week to discuss the issue and was "noncommittal" about the bill's future.

The loss of Lib Dem support would place a question mark over the future of the bill as the Conservatives would struggle to push it through Parliament alone.

Labour accepts there is an issue to be addressed but has not yet said if it will support the bill.

A joint committee of MPs and peers has been considering the draft bill since the summer and it will publish next week what is expected to be a strongly critical report.

One senior Lib Dem minister said: "The report gives Nick an opportunity to kill the bill for good and that's what he wants to do." Another said: "This is a dead duck. It is a question of when, not if."

In its report, the joint committee on the draft Communications Data Bill will argue that:

The Home Office has failed to make the case for the new laws, not least by failing to show how the police use existing laws to monitor mobile phone data.

The bill infringes civil liberties and invades privacy by allowing the police access to a mass of new data without adequate safeguards. In particular, they will argue that in some internet use - particularly social media sites - it is difficult to distinguish between the details of the communication and the actual content of the message.

The measure would damage British businesses by forcing phone companies and internet service providers to store at huge cost for 12 months masses of new data that they would not otherwise keep.

The new pool of data would be open to abuse and present a security threat.

One committee source said: "It is critical of the approach the Home Office initially took and recommends more caution and a more proportionate way forward.

"It worries about individual liberties and principle and the costs and proportionality of what was initially recommended. How secure is this information? Are you certain it cannot be stolen by people who have access to it?"

The Lib Dem leadership has faced some internal criticism for supporting separate plans in the Justice and Security Bill to extend the use of so-called secret courts to hear sensitive intelligence material.

So some within the party argue that Mr Clegg should oppose the Communications Data bill to reaffirm the Liberal Democrats' civil liberties' credentials.

Some Lib Dems believe that there is not much depth of support for the bill among the Conservatives and they will not go to the wire to save the measure.

One source claimed that even some Home Office ministers have doubts. They also noted that the Conservatives had opposed measures like this in their election manifesto, promising that they would "scale back Labour's database state".

But Home Office sources insisted that the government remained determined to get the bill onto the statute book by 2014.

They said the police were crying out for this new system which was a vital tool not just to detect crime but also to prosecute criminals.

The Conservative MP Dominic Raab said that he too would oppose the Communications Data Bill. "There are fundamental issues of necessity, principle, cost and viability that remain unanswered," he said. "I cannot see Parliament backing the plans."

Nick Pickles, director of the civil liberties group Big Brother Watch, said: "If the committee finds, like 90 day detention and ID cards before, that the Home Office is relying on scant evidence and scaremongering, both sides of the coalition should want to stop a bill that would hurt privacy, the economy and internet security.

"Parliamentarians of all parties should heed the advice of this in-depth investigation and recognise the serious concerns identified in evidence to the Joint Committee. If the committee finds this bill is not fit for purpose, I'd expect the Lib Dems to be supported by their Conservative colleagues in heeding that advice."