The reform, embarked upon two years ago, was initially opposed by legal groups who warned up to a third of people injured in crashes will lose the right to benefits after six months from the date of their accident.

The government undertook further consultation and a bill passed in April with the in-principle support of the legal profession.

However, a regulation published on Wednesday by finance minister Victor Dominello has sparked fresh criticism.

The regulation defines what constitutes a "minor injury" under the scheme, which insures motor accident victims via compulsory third party insurance.

Under the Act, those suffering minor injuries - such as whiplash - are covered for up to six months of payments to cover lost income and medical expenses.

However, NSW Bar Association president Arthur Moses said the new regulations would "significantly reduce the rights of many innocent car crash victims".

"The regulations exclude injured people with moderately severe injuries which manifest in neurological damage from access to damages, even if those injuries prevent them from returning to work," he said.

"This approach has been adopted in spite of the acknowledgement by medical specialists, during the consultation process that such injuries are genuine and can be disabling."

Mr Moses also took issue with several points of dispute in the regulations, which he said "can only add to scheme costs and red tape".

"As many injured people are unlikely to have access to a lawyer, the new system may be practically impossible for non-lawyers to navigate and create unnecessary expense and delay," he said.

"Injured motorists with no access to lawyers will be involved in unequal contests up against insurance companies and the resources such companies can bring to bear in disputes."

Mr Moses said the NSW Bar Association "cannot support these aspects of the new system which undermine the legal rights of people injured in motor accidents".

"We urge the Government to reconsider its position and adhere to the Minister's promise of providing adequate compensation to accident victims," he said.

Mr Dominello said the government had consulted with the legal profession for the past 18 months.

"Since the legislation passed Parliament in April, I have held regular Ministerial Implementation Group meetings to work through the rules of the new scheme," he said.

"An agreement was reached in July with members of the MIG on the definition of minor injury. The Government has committed to reviewing the effect of the minor injury threshold at the two year mark of the new scheme."