Revised WA budget surplus hits record $6b

WA Premier Mark McGowan says his government is using its financial strength responsibly. (Lukas Coch/AAP PHOTOS) (AAP)

Western Australia's budget surplus has reached a record $6 billion despite a fall in mining royalty revenue and infrastructure cost pressures.

Treasury figures released on Wednesday revealed a $344 million boost to the state's bottom line since the budget was delivered in May.