WA auditor-general Colin Murphy has blamed inaccurate data for the poor assessment record of the state's controversial, $450 million-a-year land tax which resulted in 10 per cent of assessments being reissued this financial year alone.

WA auditor-general Colin Murphy has blamed inaccurate data for the poor assessment record of the state's controversial, $450 million-a-year land tax which resulted in 10 per cent of assessments being reissued this financial year alone.