A government MP has broken ranks with the prime minister over a push for mandatory prison time for illegal gun traffickers.

Tony Abbott wants parliament to approve legislation that would jail those involved in the trade of illegal firearms for at least five years.

"I'm not a big fan of mandatory sentencing," Nationals MP Andrew Broad told reporters in Canberra on Monday, adding Australia already had robust and strong gun laws.

Attorney-General George Brandis says the government is acting on the advice of federal police and it is up to parliament to stipulate the sentencing range.

"Of course I have faith in the courts but that's not the point," he told reporters.

Labor senator Doug Cameron says the better option is to maintain a strong judicial system and police force.

Fellow opposition frontbencher Michelle Rowland says Labor would consider the legislation when it was re-introduced to parliament.

But shadow attorney-general Mark Dreyfus already has indicated Labor will not support mandatory sentencing.