SASKATOON - Prime Minister Stephen Harper says he would restrict the use of house arrest and force criminals to do more time in prison.

But he's not saying how much it would cost to build all the new prison spaces that would be required.

Harper says that if he's re-elected, he will end house arrest for 30 serious crimes, including robbery, theft, and arson.

Judges could still choose house arrest - officially known as conditional sentencing - for hundreds of other crimes, the Tories say.

When asked how many new jail cells would be needed, Harper said the number is `not enormous' and the cost would be `small and manageable.'

The Tories say over 11,150 criminals were serving conditional sentences in 2006, including 2,791 convicted of violent crimes.