A Turnbull government crackdown on welfare fraud has netted $1.4 billion for the budget bottom line over the past 18 months.

From July 2016 to the end of last year, the human services department investigated more than 1400 cases of potential welfare fraud, asking prosecutors to pursue 956 of these.

One case ultimately resulted in a person who used an alias to illegally claim $160,000 in disability support pensions being sent to jail for three years.