Home Affairs Minister Tony Burke has challenged the Coalition to put real numbers on its deportation plan, saying the price tag runs into the billions. His comments came as the government opened a fresh line of attack on Angus Taylor's migration pitch. Burke described the scheme as a multibillion-dollar pledge offered without any costing to back it up. Pressed on whether Labor had erred in its own handling of migration, he refused to concede any mistakes. The dodge suggests Labor wants the argument fixed on the Coalition's arithmetic rather than its own record. Taylor's side has maintained that firm enforcement is needed to bring order back to a strained system. Question time is likely to carry the fight through the rest of the sitting week.