From our payroll expert. Hope this helps.
This all hinges on who is seen as the employer.If the contactor is an employee of the temp agency, then the only employer liability would be based on the contact between the client and the temp agency.
What makes this situation a little unclear are the references to an “offer letter” and “no written contract”. Usually, a temp agency would have a written contract with its clients.
If there is no written contract in this situation, the temp agency may want to go after the client for any notice owed to the employee.
Ontario is a little unusual in that there is a 1 week notice required to employees when an assignment with a temp agency is ended before the expected end date.