Britain's ability to prevent terrorist attacks is hampered by outdated laws that are "no longer fit for purpose," a former MI5 chief said in an interview published on Sunday, as the government considers new powers to monitor the Internet.

Jonathan Evans, director-general of MI5 from 2007 to 2013, said laws should allow the intelligence services to properly monitor possible threats to national security.

Islamist gunmen killed 17 people in Paris earlier this month, pushing enhanced anti-terrorism laws up the political agenda in Britain. Britain is on its second-highest threat level, meaning an attack is considered highly likely.