The absence of an expected toughening-up of the Petroleum Resource Rent Tax regime in the federal budget has left oil and gas producers in limbo, with industry chiefs warning the uncertainty is clouding the future of more than $50 billion of proposed projects off the north-west coast.

Expectations across the sector were widespread that the 2018 budget would include a crackdown on allowable deductions under the PRRT, although with existing projects to be exempted.