The government had to significantly water down its planned changes to the Fair Work Act in order to gain crossbench support, with only three of its nine proposed changes making it through.

One of the amendments to pass the Senate on Tuesday was changes to greenfield agreements between employers and unions on large scale resource and construction projects.

The amendment would allow the employer to take an agreement to Australia's Fair Work Commission if a deal can not be struck with unions within a certain time frame.

However, the amendment did not make it through unscathed, with the government making changes to extend the timeframe from three to six months and to impose two-yearly reviews of the rules.

Despite the changes, the passing of...