Gun owners must take better care of their firearms to stop them falling into the hands of jihadists plotting a massacre, police have said, as they disclosed 800 lawfully-held weapons go missing each year.

The threat of terrorists getting guns for a marauding Paris-style assault has meant the need to rid the streets of weapons has “never been a more significant priority”, senior officers said.

The difficulty of finding guns in the UK has given police a “massive advantage” in stopping atrocities such as those seen in France, but there are concerns firearms are still available to potential terrorists, some of Britain’s most senior police chiefs have said.