The CEO of Australian Industry Group, Heather Ridout has warned of the difficulties ahead, if the Fair Work Amendment Bill does not pass through Senate this year.

The Fair Work Amendment (State Referrals and other Measures) is currently before the Senate.

The Ai Group said it understands agreements reached between the Federal and State Governments outside of the Bill have been signed and are not open to renegotiation.

"Ai Group strongly supports a completely national IR system achieved through the referral of State powers," Ridout said.

"This has been a longstanding policy position of Ai Group which we have pressed for decades.

"Therefore, while Ai Group maintains a number of concerns about the understandings reached and the potential difficulties for future amendments to the Fair Work legislation, the egg cannot be unscrambled and consequently, this should be recognised in the current debate in the Parliament."