FILE PHOTO: Chad President Idriss Deby addresses the media after a meeting with German Chancellor Angela Merkel at the Chancellery in Berlin, Germany October 12, 2016. REUTERS/Stefanie Loos/File Photo - RC13ED8061C0

N’DJAMENA (Reuters) - 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 Chad, an ally of Western nations fighting jihadist groups in West Africa.

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.