Mick Creedon, who runs Derbyshire Police, said controversial proposals debated this week were about ensuring existing powers used "all the time" by police investigations were preserved as technology improved.
He told the BBC Radio 4 Today programme: "The point is the world of policing, investigating serious crime and terrorism, and actually protecting vulnerable people, depends to a certain extent on accessing some things like core data. The safeguards in place are two fold."
Liberal Democrat president Tim Farron vows the party would "kill" proposals for increased monitoring of emails and internet use.
Ministers are preparing a major expansion of powers to monitor the email exchanges and website visits of every person in the UK.