The federal government's new gun trafficking laws are too weak and unlikely to lead to any prosecutions, NSW Premier Barry O'Farrell says.

The new offence of "aggravated trafficking" contains a threshold of 50 illegally imported firearms over a period of six months.

But on recent prosecutions in NSW, no one would be captured, Mr O'Farrell said.

"The NSW government believes the number of weapons should be substantially lower and the timeframe for trafficking extended to 12 months," he said.

"My concern is the bar has been set so high that no one will ever be prosecuted under these laws."

In a submission to the Senate inquiry that examined the laws, the NSW government revealed that in an examination of prosecutions for the sale of illegal firearms in NSW since 2008, the maximum number of firearms involved was 25 over a period of 12 months.

The law was passed in the lower house on Tuesday along with other gun legislation that could equip Australia's police with powers to target unexplained wealth and seize property and other proceeds of crime.