The former treasurer Wayne Swan said the big miners would pay at least A$2 billion tax, and wrote to the head of BDO Accounting, who modelled the claims Forrest used, noting they were "utterly unrealistic" and riddled with errors. Treasury concurred that they would be unable to release the assumptions underpinning its forecasts, as they were based on confidential information provided by the big miners. Gillard struck a deal with BHP Billiton, Rio Tinto and Xstrata to develop the MRRT. Independent MP Andrew Wilkie requested the government take Forrest's mining tax grievance to heart.