The Abbott government's overhaul of public service workers' compensation looks set to be hostage to the volatile Senate crossbench with Labor and the Greens both saying they are suspicious of the reforms.
Both parties say they suspect the reforms being pushed by Employment Minister Eric Abetz will strip entitlements from 160,000 public servants.
Without the votes of Labor or Greens senators, the government will need to convince the independent and minor party members of the upper house, who have shown little inclination so far to co-operate with the Abbott government.
Prominent compensation lawyers and one of their peak groups have already attacked the proposed changes to the Comcare scheme, saying they are an attack on the entitlements of public servants, underpinned by a dishonest campaign targeting individual workers.
Now political opposition to the bill is building with the main public sector, the Labor-affiliated CPSU, confirming that it is lobbying the ALP and the Greens to shoot down Senator Abetz's Safety, Rehabilitation and Compensation Bill.
The union says it wants to broaden the campaign, saying more than 250,000 employees in a range of industries outside the Australian Public Service are facing the loss of compensations entitlements if the legislation goes through.
Senator Abetz says his legislation reforms will crack down on public servants seeking payouts for questionable "treatments" like week-long yoga retreats or grass-cutting services.
But Labor support for the legislation looks unlikely with opposition Employment spokesman Brendan O'Connor saying his party does not trust the government with the entitlements of 160,000 public servants.
The opposition frontbencher told The Canberra Times that Labor had not finally made up its mind on the reform package but that some of the changes in the bill would directly or indirectly put workers in danger.
"Labor distrusts the Abbott Government when it comes to supporting injured workers," Mr O'Connor said.
"The Government has already proposed changes to the Comcare scheme that will directly and indirectly risk the workplace health and safety of Australian workers
"Labor supports schemes that focus on getting people back to work with appropriate support."
Senator Abetz's office did not respond to requests for comment.
Greens employment spokesman Adam Bandt said his party was "sceptical."
"We'll work through the detail, but whenever the Abbott government has tried to touch Comcare so far, it's been about weakening protections and compensation."
CPSU national secretary Nadine Flood said her union was flatly opposed to Senator Abetz's bill and would be lobbying hard to try to ensure its failure.
"The CPSU vigorously opposes any scheme that leaves an injured worker worse off and, in its current state, the 'Improving Comcare Scheme' bill does exactly that," Ms Flood said.
"We will be asking Labor, the Greens and crossbenchers to oppose any moves that will reduce the rights of injured workers.
"The CPSU has long advocated improvements in injury prevention in the workplace and early intervention in getting people back to work as more appropriate ways to improve the Comcare scheme."
Ms Flood also signalled a move to broaden the campaign beyond the public service.
"The Comcare scheme is an issue for workers in many industries and we are working with the ACTU and other unions to coordinate a response to any threat posed to the workplace health and safety of workers," the union official said.