"Edem Kodjo is named prime minister," Gnassingbe said in a presidential decree read on state television.
Kodjo was prime minister from 1994-96 under Gnassingbe's late father, whose authoritarian rule lasted almost four decades. He is a former secretary-general of the Organisation of African Unity, the forerunner to the African Union.
Togo plunged into crisis in February when Gnassingbe's father, Africa's longest serving leader, died and the army named Gnassingbe to replace him in violation of the constitution.
The softly spoken business graduate later stepped down after violent protests and an international outcry but won April elections which the opposition said were rigged.
Gnassingbe had offered to form a coalition government with Togo's main opposition parties but late on Tuesday he categorically rejected their demands, saying they would effectively cancel his constitutional powers.
The six so-called "radical" opposition parties had pushed for a prime minister chosen from among their ranks.
Kodjo is head of the moderate CPP opposition party, which is not part of the main opposition coalition that united behind a single candidate to challenge Gnassingbe in the April polls.
More violent street protests by opposition supporters followed the vote, triggering a heavy-handed crackdown by security forces and causing some 33,000 people to flee to neighbouring Ghana and Benin.
Togo's Human Rights League has said 800 people were killed in the unrest although Western diplomats have said they believe between 100 and 150 lost their lives.
- Reuters - Thomson Reuters Foundation
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