The huge growth in internet telephone traffic is jeopardising the capability of police to investigate almost every type of crime, senior sources have told The Times.

As more and more phone calls are routed over the web – using software such as Skype – police are losing the ability to track who has called whom, from where and for how long.

The key difficulty facing police is that, unlike mobile phone companies, which retain call data for billing purposes, internet call companies have no reason to keep the material.

Jacqui Smith, the Home Secretary, outlined plans yesterday for a huge expansion of the Government’s capability to access data held by internet services, including social networking sites such as Facebook and Bebo, and gaming networks.

The move follows growing concern among police and the security services that serious criminals and terrorists are using websites as a way of concealing their communications.

At present security and intelligence agencies can demand to see telephone and e-mail traffic from communication service providers, such as mobile telephone companies. But rapid expansion of new providers, such as gaming, social networking, auction and video sites, and technologies, such as wireless internet and broadband, present a serious problem for the police, MI5, Customs and other government agencies.

Communications data is now a key weapon in securing convictions of both terrorists and serious criminals. It also plays a central role in investigations into kidnappings and inquiries into missing and vulnerable people.

In the Metropolitan Police service alone last year, 54,000 applications were approved for officers to have access to communications data including to whom and when a phone call, text message or e-mail was sent – but not the content. A total of 650 applications concerned investigations into tracing missing or vulnerable people.

“Communications data forms an important element of prosecution evidence in 95 per cent of serious crime cases,” a security source said. “We could not begin to start to solve any kidnap in this country without access to the data.”

Overall there were 519,260 requests for communication data last year with the vast majority coming from the intelligence services, police and other law enforcement organisations, such as the Serious Organised Crime Agency and HM Revenue & Customs.

Under Ms Smith’s plans, police and the security services will not be able to access the content of the communications but will know each website visited, and to whom and when a phone call was made or a text message or e-mail was sent. If this raises suspicions, ministerial approval can be sought to intercept what is being sent and read the content.

The police and the security services say that it is becoming difficult to locate data because there are now so many communication service providers. The use of multiple user names is also thwarting efforts to identify individuals.

In a speech to the Institute for Public Policy Research yesterday, the Home Secretary said that changing technologies were presenting challenges to collecting data. A consultation paper next year would outline “some way or other to collect that data and store it”. Legislation could follow later in the year or in 2010.

Ms Smith said: “The communication revolution has been rapid in this country and the way in which we intercept communications and collect communications data needs to change too. If it does not, we will lose this vital capability.”

She gave warning that the alternatives to more electronic data being stored would be expensive and invasive. “If you want to maintain your ability to identify where the user of a mobile phone is, let’s say . . . it may well be that the only other alternative to collecting that data would be a massive expansion of surveillance and other intrusive methods of tracking.”

The Times has learnt that police chiefs are to begin a discreet lobbying exercise in favour of the new powers. “This is a hugely important issue,” a senior source said. “To lose the capability to collect phone data would be disastrous.”

Opposition MPs and privacy groups attacked any further extension of state power as Orwellian. A leaked memo written by sources close to the so-called interception modernisation programme said that officials in the Home Office viewed a giant database as “impractical, disproportionate, politically unattractive and possibly unlawful from a human rights perspective”.

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