More than 20 people have been warned by Lancashire Police that their lives were under threat in the last three years.
The force issued three so-called “Osman warning” letters in 2014, compared to 13 the year before. Eight were issued in 2012.
The “threat to life” notices are issued by police forces to warn somebody they may be in danger from a real and immediate threat.
Police chiefs say the warnings, which were started after businessman Ali Osman was shot dead in east London in 1988 by a teacher who had previously said he was thinking of committing a massacre, are “one of a number of options” used to deal with threats to life.
A National Police Chiefs’ Council spokesman said: “Osman warnings have proved highly effective in the overwhelming majority of cases.”