Major submarine maintenance is likely to stay in Adelaide, thanks to a combination of political pressure and budgetary constraints, with the Morrison government risking the ire of Western Australia over missing out on $400 million a year of taxpayer-funded work.

Defence industry sources believe Prime Minister Scott Morrison has little appetite for the move, as key crossbench Senator Rex Patrick renewed his warning that taking away the 700 submarine jobs from South Australia was a red line and could jeopardise his willingness to co-operate with the government on legislation.