The appointment of a civilian as police commissioner is an insult to the country's police force, the SA Policing Union (Sapu) said on Wednesday.
"We were of the opinion that the president would [have] learnt that non-police officers have not made any good national police commissioners," Sapu general secretary Oscar Skommere said in a statement.
"The continued imposition of others in the top SAPS (SA Police Service) office is not only an insult to tens of deserving officers, but it also demoralises them."
President Jacob Zuma announced on Tuesday that business executive Mangwashi Victoria "Riah" Phiyega would replace Bheki Cele as police commissioner.
Skommere said the SAPS was a "military environment" and it deserved to be kept that way.
However, Sapu would respect Phiyega's appointment and was willing to work together with her.
"We also want to state it categorically... that as professionals we are willing to work with whomever is in that office, including the new national police commissioner," he said.
"We call upon all SAPS officers as disciplined men and women in blue to give the new national commissioner the necessary support in her new office."
Phiyega currently chairs the presidential state-owned enterprises review committee and is a director at Tsa Rona Investments.
The Polokwane-born executive previously held positions in the corporate sector, including Absa. Prior to that, she served on the boards of Transnet and the Port Management Association of Eastern and Southern Africa.
She was part of the 2010 Soccer World Cup bid committee and received a special award for her work. The University of Limpopo bestowed a community work leadership award on her.
Phiyega has several tertiary qualifications in business management and social work. She is also known for her community work with women and children.