The homestay company that placed an Islamic State-inspired terrorist with a Melbourne family is facing a lawsuit for failing to warn them she had practised her stabbing attack using a mattress from another host family.

Bangladeshi woman Momena Shoma pleaded guilty in September to engaging in a terrorist act, after she stabbed Roger Singaravelu in the neck as he napped next to his five-year-old daughter in the rumpus room of his Mill Park home.

Momena Shoma's passport photo.

Shoma is yet to be sentenced over the attack, however Mr Singaravelu is suing Australian Homestay Network for loss of earnings and other damages after the company contacted his family in February asking that they urgently host the Bangladeshi international student.

According to a writ filed in the Supreme Court earlier this week by Mr Singaravelu's lawyers, the company knew or should have known that Shoma posed a safety risk because her first host family had noticed she was acting erratically, including using a knife to stab a mattress.