The Tories have attacked the government's move to create a database that tracks all Britons' journeys in and out of the UK.
The database - to be operated from a Manchester location - will store 250 million journeys made by individuals in and out of the UK each year, with details kept for up to 10 years.
The government says the database is needed in the fight against crime, illegal immigration and terrorism.
The Manchester intelligence centre will store the names, addresses, telephone numbers, seat reservations, travel itineraries and credit card details of all travellers.
Shadow home secretary Chris Grayling said, "The government seems to be building databases to track more and more of our lives.
"The justification is always about security or personal protection. But the truth is that we have a government that just cannot be trusted over these highly sensitive issues. We must not allow ourselves to become a Big Brother society."
The Tories concerns were echoed by the Liberal Democrats.
The database is part of the e-Borders scheme, and covers flights, ferries and rail journeys.
The Home Office says similar schemes are run in other countries, including the US, Canada, Spain and Australia.