Montana senators have endorsed a proposal to double DUI fines.

Seven Democrats joined 20 Republicans Saturday to approve House Bill 488 on a 27-23 vote that reversed the Senate's Friday opinion against the bill.

The Republican proposal would double minimum fines for driving under the influence and clarify that the same penalties apply to people driving high on marijuana. It would also levy a $300 fine on anyone believed to be driving under the influence who refuses to submit to a drug test.

Supporters say Montana is one of the nation's least punitive states in DUI penalties and a high rate of DUI recidivism compels change.

Opponents say the fines likely won't deter repeat offenders.

The proposal faces another vote in the Senate.