Critics of President Deby say the constitutional changes are aimed at installing a de facto monarchy. Parliament approved the changes 132-2, after most of the opposition boycotted the vote.
Chad's parliament on Monday overwhelmingly approved a new constitution that expands President Idriss Deby's powers and could allow him to stay in office until 2033, in a vote boycotted by most opposition lawmakers.
The new constitution reimposes a two-term limit scrapped in a 2005 referendum. But it will not be applied retroactively, meaning Deby could serve two terms after the next election in 2021.
The constitution now heads to Deby for his signature.
Deby's opponents say that the constitution, which eliminates the post of prime minister and creates a fully presidential system, is aimed at installing a de facto monarchy in the central African country and ally of primarily Western nations fighting Daesh-linked groups further west.
The new constitution – approved by a vote of 132 to two – introduces six-year rather than five-year presidential terms. That would mean Deby could stay in power until 2033, when he will be at least 80.
Deby first came to power in a rebellion in 1990. He has recently faced strikes and protests due to budget shortfalls caused by low prices for Chad's chief export, oil.