VANCOUVER -- A civil rights group in B.C. has released a report that says mandatory minimum sentences imposed by the Conservative government will cost billions of dollars without reducing crime.

The B.C. Civil Liberties Association says the federal government should instead be moving away from mandatory minimums, or at the very least include exceptions that allow lower sentences in some circumstances.

The report says the federal government has added dozens of new mandatory sentences in the past 10 years, which has led to dramatically increased costs for courts, lawyers, prisons and parole officials.

However, the report says there is no proof that mandatory minimums have any effect on crime, and instead it argues longer prison sentences mean that some offenders are more likely to offend once they're released.

Report author Raji Mangat says courts have already ruled that some mandatory minimum sentences are unconstitutional, and she says her group hopes to intervene in a case that's expected to be heard by the Supreme Court of Canada in the fall.

The Conservative government has added minimum sentences to a range of crimes, including drug and gun offences.