EU ministers want to make it easier for personal contents to be searched "remotely" without a warrant.
Top cops will give authorisation if they believe it is "proportionate" and necessary to prevent serious crime.
But Shami Chakrabarti, of human rights group Liberty, is preparing to challenge the legal basis of the move.
She said: "These powers are as intrusive as someone busting down your door and coming into your home.
"This is a devastating blow to personal privacy and needs to be controlled by legislation and judicial authorisation."
The Home Office said it is working with other EU states on details of the proposals.