Outgoing South Australian Premier steps down as Liberal leader after election defeat

South Australian premier Steven Marshall will step down as leader of the state's Liberal Party after Labor swept to victory in this weekend's election.

Marshall will remain MP for Dunstan, he said.

"Whilst I am disappointed by the election outcome, I take full responsibility for the result and accept the will of the people," he said in a statement.

READ MORE: Who is Peter Malinauskas? The trolley boy turned next SA Premier

"It is time for someone else to lead the team into the future," he said, adding he will leave the party leadership role after nine years, as soon as his successor is elected.

He added the state "faced the most extraordinary of times, through natural disasters and a global pandemic" under his premiership.

By late on Saturday night, Labor had won at least 25 seats, one more than is required to form a majority government.

This morning, Prime Minister Scott Morrison defended Marshall's campaign.

"Steven Marshall turned the state of South Australia around, he turned their economy around, he brought business back to South Australia, he created a new buzz in South Australia, which was drawing investment, technology firms, securing important events industry for his state," Mr Morrison said.

READ MORE: Morrison deflects Liberals' defeat in SA away from federal election

The state's new premier is set to be Peter Malinauskas.

The Labor leader is a 41-year-old father of three.

Mr Malinauskas started his working life as a trolley boy for Woolworths at age 15, before being promoted to the checkout.

He only entered the lower house at the last election in the seat of Croydon in Adelaide's north west.

Mr Malinauskas ran as the change candidate, focusing heavily on healthcare.