Spying laws 'one of the most important pieces of legislation' during parliament

The new spying laws published tomorrow will be "one of the most important pieces of legislation" considered by MPs over the next five years, David Cameron told ministers.

The Prime Minister said the package of measures "goes to the heart of the Government's duty to keep the British public safe".

His comments came as the Cabinet was briefed about the Investigatory Powers Bill covering the tools available to police and intelligence agencies to fight terrorism and serious crime in the digital age.

In a potential area of controversy, measures requiring internet firms to store internet connection records (ICR) to respond to the increasing use of apps and social media for communication are expected to be included in the draft Investigatory Powers Bill.

However, sources said access to ICRs will be controlled and they will not include a full browsing history or reveal every web page visited, with strict limits on accessing the records.

Security services will retain the capacity to intercept the content of communications after obtaining a warrant.

It is understood that ministers have ruled out any proposal to restrict encryption or ban it, despite fears in the intelligence community that advanced online security measures risk leaving them locked out of some areas of cyber space.

The Prime Minister's official spokeswoman said Home Secretary Theresa May talked colleagues through the powers contained in the legislation.

The spokeswoman said: "The Prime Minister underlined that this is about maintaining the agencies' current capabilities, that this is about - in a nutshell - the powers we need to keep us safe and about increasing public confidence in what they do in the process."

Mr Cameron told ministers "this would be one of the most important pieces of legislation during this parliament because it goes to the heart of the Government's duty to keep the British public safe".