The new motor accident injuries commission bill will finally be debated by the ACT's parliament next week after the legislation was amended to allow injured children and workers to pursue common law damages in more circumstances.

But Unions ACT says the new scheme will substantially reduce rights for workers injured in a crash.

Unions ACT secretary Alex White said the impact on injured workers was not something considered by the citizen's jury which determined the shape of the reforms, and unions have not been consulted about the changes.

"They may have spent 18 months talking about it but they haven't talked to the unions about reducing workers rights," Mr White said.

A government spokeswoman disputed this, saying there had been ongoing discussions with stakeholders - including Unions ACT - on top of the citizens’ jury process, the release of an exposure draft bill and a full inquiry by the Legislative Assembly’s Justice and Community Safety Committee.

"We understand that these are significant reforms, which is why we have been carefully working through them for almost two years," she said.

But unions are particularly concerned about workers injured on the roads being forced to opt into either the workers compensation scheme or compulsory third party insurance scheme after 13 weeks.

The government spokeswoman said this had been extended from one month in response to union concerns.

But under current arrangements, a worker injured on the road can change scheme at any time and one scheme pays back the other to prevent double dipping. Having to choose early could have a "negative impact on workers’ recovery, wellbeing and income", Mr White said.

But the bill also introduces a new concept of significant occupational impact, which will measure how an injury affects a person's ability to keep doing their job.

It will apply if a worker has been receiving income support for four-and-a-half years after their accident, but they did not meet the injury threshold to sue for common law damages. The assessment will be used to determine whether the injury has had a significant impact on the person's ability to be employed.

Mr White said this was done without consultation with unions and creates a standard that does not exist anywhere else in the world.

He also said the assessment will be conducted by a medical examiner determined by an insurance company, not the injured person’s treating doctor, and as drafted the bill significantly restricts compensation for a worker who is injured in a road accident and is unable to return to work.

"This is worse than what it was originally going to be as far as workers rights are concerned," Mr White said.

“While the government may say the changes are generous, the truth is that injured workers will have fewer rights and fewer options under the proposals.

“There is no need for this haste, and there has been no effort made to explain or justify why workers should have their rights reduced."

However, an ACT government spokeswoman said they had "heard and responded" to union concerns about how the new scheme will affect workers.

She said the ability for workers to make a common law claim if they have been unable to re-train or return to work after their accident "further strengthen the scheme in relation to protections for workers who are injured on the road".