"There are a series of important bills before the parliament as well as some problematic recent court rulings that are challenging and which will require the early attention of the new minister," Mr Willox said.
Ai Group earlier in the month criticised a landmark Federal Court ruling, which granted annual leave entitlements to a casual worker.
Australian Council of Trade Unions secretary Sally McManus believes Mr Morrison is a bigger threat to workers than his predecessor Malcolm Turnbull, who was knifed by the Liberals on Friday.
"He will be ruthless," Ms McManus told the ABC on Sunday night.
"He does not listen to the real situation that most working people are in where their wages are going backwards and their jobs are insecure."
She said the union movement had already had a boost in volunteers correlating with the Liberals' leadership crisis.
"We are going to double down now," Ms McManus said.
Meanwhile, Ms O'Dwyer says she's happy industrial relations is back in cabinet.
"A productive and flexible workforce is a key plank in building a stronger economy," she said in a statement on Monday.
"But more importantly, creating the framework for a productive working environment between employers and employees is critical for our nation to grow and prosper."