The decision comes after the state government restored some of the benefits it took away from injured workers under its WorkCover reforms in 2012.

However, the government ignored warnings from the WorkCover Independent Review Office when it amended the workers compensation scheme earlier this month, introducing changes which increased benefits for people with the most serious injuries and those needing hearing aids and prosthetic limbs who lost benefits in 2012.

However, for the vast majority of people with less serious injuries needing continuing  medical treatment, WorkCover Independent Review Officer Kim Garling warned that access to benefits would be more difficult.

"Where the insurer disputes whether the treatment is reasonably necessary there are instances where the compensation period expires before a decision is made by the Workers Compensation Commission or on appeal to the court," he said.

Mr Garling was also concerned that injured workers would no longer be assessed for their long-term needs, based on their level of permanent impairment. Instead, they will be given only one assessment which means if their condition deteriorates at a later date, or after surgery, they will not be able to ask for an increase in their lump sum compensation payment.

A NSW Court of Appeal decision in Cram Fluid Power v Green on Thursday has confirmed that injured workers will not be entitled to make a further lump sum claim if their condition worsens.

Patrick Scala, from Shoalhaven Heads, said he was "shattered" to learn on Friday that he will have no further entitlement to a lump sum payment.

He injured his lower back on three occasions between 2005 and 2008 when he was working as night filler packing shelves at a supermarket. He received a lump sum payment in 2009 and has not worked since 2007.

"My condition has got worse since 2007 but the door has been slammed shut," he said.

"In the last three years, I've had two hip replacements and back surgery and am going in for another one on the 9th of September because the first surgery failed," he said.

Sydney teacher Dianne Denton injured her right shoulder in a fall in late 2013 and after the pain became progressively worse, a specialist doctor recommended surgery earlier this year. But because she can only qualify for payments for medical expenses for two years from the date of her injury under the government's latest amendments, her window will expire in October.

"I am disappointed that ...the insurer automatically said sorry, we cannot open your case," she said.

NSW Greens MP David Shoebridge said the Court of Appeal decision meant that once an injured worker had their level of  impairment assessed "they are stuck with that assessment forever, regardless of any serious deterioration or surgery that has made their injury significantly worse".

"The effect of this is that thousands of workers are prevented from getting access to necessary medical treatment and income support."

NSW Finance Minister Dominic Perrottet said the government was committed to a workers compensation scheme that is "fair, sustainable and places the injured worker at the centre".

"[T]he 2015 insurance reforms passed this month will see $1 billion of benefits and premium reductions distributed to injured workers and business."

A WorkCover NSW spokesman said it was reviewing the Court of Appeal decision which relates to the 2012 changes.

He said the government had considered advice on the 2015 reforms from a range of stakeholders.

"The assessment of whole person impairment for an injured worker is intended to occur once the injured worker's condition has stabilised," the spokesman said.

"Any potential for delays in treatment associated with ongoing legal disputes should be mitigated by the extension of medical entitlement time periods, a feature of the recent changes to the workers compensation system."

Australian Lawyers Alliance spokesman Anthony Scarcella said he welcomed the government's decision to restore extra resources to the workers compensation scheme.

However , he was "troubled" by the changes to the entitlement to payment of medical expenses.

"There are many conditions that result in significant levels of impairment that require little treatment. The government has recognised this by providing lifelong assistance with hearing aids, batteries, and other aids," he said.

"On the other hand there are many conditions, such as non-surgical back injuries, that result in little impairment but require significant ongoing treatment to support a worker continuing to work. The legislation also fails to recognise that the level of impairment can increase over time as a result of a deteriorating condition or subsequent surgery."