Negotiations between the government and the Greens to pass the controversial $3 million super tax risk becoming complicated after the shock defection of WA senator Dorinda Cox to the Labor Party.

Cox’s defection came just an hour after Greens senator Sarah Hanson-Young suggested the minor party could compromise on its demands the government drop the threshold for the proposed super tax to $2 million and index it. “We will be constructive and look for an outcome that is best for everybody,” Hanson-Young said.