UKIP leader Paul Nuttall has suggested the detention without trial of suspected terrorists.
Mr Nuttall said he was not calling for an immediate return to internment, but "wouldn't take anything off the table".
Speaking to the BBC's Andrew Neil, he backed the return of the death penalty but said this was not UKIP policy.
In the interview, to be broadcast at 19:30 BST on BBC One, he insisted there remained plenty for his party to fight for after achieving its Brexit goal.
UKIP won the third highest number of votes in the 2015 general election - 3.8 million - but this gave it just one MP, who subsequently quit the party.