The Tories yesterday pledged £1bn over four years to tackle crime, with tagging and lie-detector tests for sex offenders and building more prisons at the top of their list.

Annabel Goldie, Scottish party leader, said US-style policies such as lie-detector tests and a "three strikes and you're out" approach to sentencing were advocated, and the Conservatives would act immediately to build another prison in Scotland.

"We know that the majority of crime in this country is drug-related," she said.su "If we are serious about reducing crime, then we have to launch an assault on drug abuse too."

The law and order manifesto pledges to hire 1500 extra police, crack down on youth crime, end automatic early release, get tough on persistent offenders, and invest £100m a year on drug rehabilitation.

Since releasing sex offenders and housing them is a source of "public anxiety", the manifesto proposes giving them truth tests and tracking them by satellite technology.

Persistent offenders handed their third jail sentence would serve additional jail time proportionate to their previous sentences.

All prisoners would have random drug tests and searches, and all drug dealers would be tried on sheriff court indictment at least to indicate the seriousness with which the crime was viewed.