No decision has been made about requiring everyone who buys a mobile phone to register their identity on a national database, says the Home Office.
Government has discussed the idea of such a register in recent talks with mobile phone operators, according to a report in the Sunday Times.
Contingency planning is thought to be under way at Vodafone for the move, which is aimed at keeping track of the owners of the UK's prepaid mobile phones, the report said.
If adopted, the register would complement the proposed central database for holding the data and time of every phone call and e-mail in the UK.
The government has given £1bn to the electronic intelligence service, GCHQ, to pilot the database, which is part of plans for a new Communications Data Bill designed to tackle terrorism and crime.
Vodafone told Computer Weekly the firm has not made any "contingency plans" to start requiring registration for the purposes of a government data collection scheme.
"Vodafone does support mandatory registration for its pre-pay customers in the UK," a spokesman said.
A Home Office spokesman said no decisions have been taken on a register of mobile phone owners.
"Of course there is a balance between privacy and our liberty which is why we have said we will be consulting on this and seeking a political consensus," he said.
Home Secretary Jacqui Smith has made a public commitment to consulting widely before drawing up new legislation.
"We also need to agree what safeguards will be needed, in addition to the many we have in place already, to provide a solid legal framework which protects civil liberties," she told the Institute for Public Policy Researchlast week.
The Information Commissioner's Office (ICO) said it welcomes the commitment to consultation and will study carefully the details put forward in any forthcoming legislation.
"It is important to highlight that creating large collections of data is not a risk free option. This not only engages concerns about unwarranted intrusion into the lives of every citizen it also raises worries aboutmaking sure that people's personal information is properly safeguarded, is not misused and can never fall into the wrong hands," an ICO spokesman said.