Unions have slammed “astounding” changes to the ReturntoWorkSA injury insurance scheme.

SA Unions has accused the state's new Labor government of trying to rush through legislation to make it harder for workers to claim compensation for multiple injuries caused by the same workplace incident.

The state government and Business SA claim changes are required to make the ReturnToWorkSA scheme more affordable for employers.

The legislation for the changes was introduced on the same day as the state budget. 

Employers pay ReturnToWorkSA premiums to cover potential work injury claims. 

Last year, a worker sought compensation for a broken leg and a hip replacement, but ReturnToWorkSA argued it was not obliged to compensate the truck driver for a limp and back pain that were also caused by his accident. 

The SA Government is now seeking changes to enshrine in law that claims for separate injuries will have to be heard in separate cases, SA Unions secretary Dale Beasley said.

“It's astounding that we are mere months from an election and the disrespect that has been shown to South Australian workers by having these changes rushed through before people have even had an opportunity to look at the legislation, let alone consider it consult and give feedback,” Ms Beasley told ABC Radio Adelaide. 

“It's just astounding.”

Workers compensation specialist lawyer Eloise Theodore said the government's bill could negatively affect thousands of workers.

“Every worker who sustains more than one injury in the course of their employment will be affected [apart from] the very few who manage to get through in the next few months and that's highly unlikely in the way the scheme operates,” she told reporters.

“The changes the Liberal government made last year were significant, but these changes blow them way out of the water.

“These changes will decimate workers' entitlements in South Australia.”