The Tories will today announce proposals to lock up children as young as 12 convicted of petty crimes such as vandalism and burglary.

The plans, to be included in the Tories' election manifesto, would see the creation of 1000 secure training places for 12 to 15-year-olds and the building of 50 institutions at a cost of £120 million.

Offenders would take classes in the institutions and will be released early if they perform well in the lessons.

Ann Widdecombe said she wanted to end the "farcical situation" in which child criminals "come back laughing from the court".