The Human Rights Commission is calling on the Government to reconsider its decision to not allow the 90-day bill to go to a select committee.
The bill, which will give small business owners the right to fire new staff after 90 days without legal challenge, is to be passed under urgency before Christmas.
Equal Employment Opportunities Commissioner Judy McGregor said rushed legislation is potentially risky legislation.
Dr McGregor said this fundamental change to employment which requires serious consideration.
The commission has sent letters to the Ministers of Labour and Justice, saying the select committee process is an important check and balance where both employers' and employees rights can be debated in a measured way.
The Engineering, Printing and Manufacturing Union is circulating a petition, urging the Governor General to delay or decline royal assent for the bill.
The petition asks the Governor General to withhold royal assent for the legislation until it has gone through the usual parliamentary processes.
Labour Minister Kate Wilkinson on Wednesday said the proposed law will give firms that are struggling against a tough economic backdrop confidence to take on new workers.
She said the bill contains safeguards for workers, including mediation and good faith provisions.
Business leaders have welcomed the bill saying the introduction of a probationary period would give employers the confidence to hire staff.