New European Union (EU) legislation which calls on internet service providers (ISP) to keep track of online activity came into force today (April 6th).
The controversial plans, which were developed after the terrorist attacks in London in 2005, call on ISPs to store data related to emails and website visits for a whole year.
Details of phone calls made over the internet are also included in the EU directive which will run alongside existing European rules which require telecoms firms to store telephone records for a minimum of 12 months.
ISPs have questioned the extra costs involved in the initiative, while privacy campaigners have also been critical.
However, a spokesperson for the Home Office, which will monitor the system in the UK, told the Telegraph: "It is the government's priority to protect public safety and national security.
"That is why we are completing the implementation of this directive, which will bring the UK in line with our European counterparts."
The government representative added that the system will apply "across the board" and not just to the largest internet providers, as first thought.