Labor is set to be returned for a fourth term in South Australia with independent MP Geoff Brock agreeing to support the party to form a minority government.

Mr Brock’s decision ends a week of uncertainty after the March 15 poll delivered a hung parliament.

In return, the mid-north MP will join the ministry, taking on the portfolios of regional development and local government relations.

Premier Jay Weatherill has thanked Mr Brock for his support and vote of confidence in Labor.

“This delivers a secure and stable government for the people of South Australia,” Mr Weatherill told reporters on Sunday.

“The inclusion of Mr Brock in our cabinet will allow us to add a strong voice for regional South Australia.”

Mr Brock has pledged to back the government on issues of confidence or supply but will remain free to vote against Labor on other issues.

“Certainly I won’t be voting against supply or to bring the government down,” he said.

Mr Brock said fundamental to his decision was the potential instability that could have resulted had he opted to support the Liberals.

With Labor holding 23 seats in the 47-seat House of Assembly after the election and the Liberals 22, the balance of power was to rest with Mr Brock and fellow independent MP Bob Such.

Labor needed the support of just one independent to form a minority government while the Liberals needed both.

But the uncertainty escalated on Saturday when it was revealed that Dr Such was in hospital ahead of surgery on Wednesday and will be taking up to two months of sick leave.

Had Mr Brock sided with the Liberals, it would have left the major parties tied at 23 votes each and the potential for a fresh election to be called.

Opposition Leader Steven Marshall is yet to respond.