Veteran South Australian MP Duncan McFetridge has formally quit the Liberal Party after losing pre-selection in his seat for the 2018 state election.
Dr McFetridge revealed his plans earlier this month but confirmed them in a statement to parliament on Tuesday.
He has held the suburban seat of Morphett since 2002, but recently lost pre-selection to former Collingwood footballer and local mayor Stephen Patterson, a move he described on Tuesday as a "completely unforeseen outcome".
He said he viewed it as a "no confidence decision" by the Liberal Party.
"I saw no point in remaining as a member of the Liberal Party and have resigned from the party," he told the house.
"It is now my intention to see out my remaining time in this place as an independent Liberal on the crossbench."
He said he has not yet decided on his long-term future but he plans to consult with his family and friends before making another announcement later.
It remains unclear whether he will contest the next election in March as an independent.
Dr McFetridge previously held a range of opposition front bench positions but was dumped as a shadow minister by leader Steven Marshall in January.
He retained Morphett in 2014 with a near 13 per cent margin, but that was reduced to an estimated 7.7 per cent in the 2016 redistribution of electoral boundaries.