SA cabinet reshuffle on merit: premier

South Australia's cabinet reshuffle will be based on merit and what is in the state's best interests, Premier Jay Weatherill says.

Mr Weatherill has confirmed his reshuffle will be finalised before parliament resumes next month.

He has refused to offer any details amid speculation new upper house MP and former union chief Peter Malinauskas will be fast-tracked into the ministry.

But he said the changes would not be based on any factional issues and he did not care if people were upset with his decisions.

"I'm interested in giving South Australians the best cabinet they need to meet the challenges we face as a state," the premier said on Monday.

"I'll approach this task of the line-up of the cabinet with one principle in mind - that's the principle of merit, having regards to what's in the best interests of South Australia."

Mr Malinauskas filled a casual vacancy in the Legislative Council late last year after the resignation of former Labor MP Bernard Finnigan who was convicted on a child pornography charge.

He was previously head of the powerful Shop, Distributive and Allied Employees' Association in SA.

Without endorsing his inclusion in the cabinet, Mr Weatherill said Mr Malinauskas would make an excellent minister.

"I'm sure there are a range of portfolios he could service in," the premier said.