OTTAWA -- An Ontario senator tired of waiting for the Liberal government to bring in its promised sentencing reforms is preparing to go ahead alone.

Independent Sen. Kim Pate says she is planning to introduce legislation that would allow judges to decide whether they should impose mandatory minimum penalties on offenders at sentencing time.

"They are in the best position to determine: is this is an appropriate place for the application of the mandatory minimum penalty?" said Pate, who was a longtime advocate for the rights of prisoners before she was named to the Senate in November 2016.

"If they determine it is not, the provisions that we are proposing will actually allow them to not impose the mandatory minimum and provide their rationale for doing so -- or not, as the case may be," said Pate.

Prime Minister Justin Trudeau tasked Justice Minister Jody Wilson-Raybould with reviewing the controversial sentencing reforms the previous Conservative government brought in as part of their tough-on-crime agenda.

Many of those changes involved imposing or increasing mandatory minimum penalties for dozens of offences -- a measure critics say prevents judges from being able to use their discretion when necessary.

The Justice Department says 68 per cent of the ongoing 256 charter challenges it is tracking are related to mandatory minimum penalties.

Pate began preparing her private member's bill last year, but held off on putting it forward as she expected the Liberal government to make good on its promise to introduce its own legislative changes.

Wilson-Raybould had committed to doing so by last fall as one way to help tackle the delays plaguing the criminal justice system, but now says she wants to take more time to get things right.

Pate said barring any signs the Liberal government will move ahead quickly, she plans to introduce her private member's bill within the next month.