• Facebook and MySpace could be required to hold data about every person users chat with for up to year • Privacy campaigners condemn 'centralised snooping'

Privacy campaigners expressed alarm today over government plans to monitor all conversations on social networking sites in an attempt to crackdown on terror.

A Home Office spokesman said that the internet eavesdropping plan, which would be set out in the next few weeks, would cover any social network that allows people to chat to one another, including Facebook, MySpace, Bebo and Twitter as well as internet calls on Skype.

He said the proposal would update existing plans to store information about every telephone call, email, and internet visit made by anyone in the UK on a central database.

"We have no way of knowing whether Osama bin Laden is chatting to Abu Hamza on Facebook. Or terrorists could be having a four-way chat on Skype," he said.

He said the government was not interested in the contents of the communication: "What we want to monitor is that so-and-so is logged on to that site and spoke to so-and-so. It's the who, when and where, not the content."

But he conceded that in "high-profile cases" the police would want to examine the contents of social network chatter. "The security service would want the ability to capture information that could lead to conviction," he said.

Under the new proposals, the sites that host social networks could be required to hold data about who users correspond with for up to a year.

Privacy campaigners criticised the plan, saying it would be another unwieldy, costly and unnecessary failure.

Shami Chakrabarti, director of human rights group Liberty, said: "The widescale use of social networking websites highlights the enormity of government ambitions for a centralised communications database for the surveillance of the entire population … Technological development is used as an excuse for centralised snooping of a kind that ought never to be acceptable in the oldest unbroken democracy on earth."

Michael Parker, spokesman for campaign group NO2ID, said the government was enforcing data sharing and the pillaging of private information. "Their plans for the intercept modernisation programme were completely unworkable to begin with and are becoming more so with every addition they suggest. The idea of tracking calls, texts and emails made by people in the country is unspeakably offensive."

The plans were first revealed by the Home Office minister, Vernon Coaker, last week at a Commons committee hearing on a draft EU directive that does not cover social networking.

He said the government's intercept modernisation programme proposals may be extended to include "the retention of data on Facebook, Bebo, MySpace and all other similar sites".

He added: "The government are looking at what we should do about the intercept modernisation programme because there are certain aspects of communications which are not covered by the [EU] directive."

Coaker acknowledged that the plan would raise fresh concerns about the right to privacy.

"I accept that this is an extremely difficult area. The interface between retaining data, private security and all such issues of privacy is extremely important," he said.

The Home Office spokesman said a consultation paper, to be published shortly before or after Easter, would explore the practicality of the plan.

In a statement the Home Office added: "The government has no interest in the content of people's social network sites and this is not going to be part of our upcoming consultation. We have been clear the communications revolution has been rapid in this country and the way in which we collect communications data needs to change so that law enforcement agencies can maintain their ability to tackle terrorism and gather evidence.

"To ensure that we keep up with technological advances we intend to consult widely on proposals shortly. We have been very clear that there are no plans for a database containing the content of emails, texts, conversations or social networking sites."

On Monday the Joseph Rowntree Reform Trust published a report claiming that a quarter of all the largest public-sector database projects, including the identity cards register, were fundamentally flawed and clearly breach European data protection and rights laws. Claiming to be the most comprehensive map so far of Britain's "database state", the report says that 11 of the 46 biggest schemes, including the national DNA database and the Contactpoint index of all children in England, should be given a "red light" and immediately scrapped or redesigned.