Hlaele told journalists in Maseru that the Public Service Commission endorsed his ministry's recommendation that Motinyane be appointed DPP in an acting capacity until further notice.
The minister described Motinyane as a "young, energetic, committed and dedicated lawyer" whose capabilities needs to be utilized.
"As young as she is, she needs exposure in order to exhaust and show case her capabilities," Hlaele said.
Motinyane is the first woman to occupy the position of DPP.
Hlaele said the government was in the process of recruiting a substantive replacement for Thetsane.
Thetsane's leave followed criticism by supporters of the current four-party coalition government led by Prime Minister Thomas Thabane after he allegedly failed to oppose the bail application by former Defence Minister Ts'eliso Mokhosi who is facing murder charges.
Thetsane was expected to retire in July 2018 after reaching retirement age of 60 years.