More than 70% of voters in Madagascar's referendum supported constitutional changes that give more powers to President Marc Ravalomanana.
Mr Ravalomanana came to power after street demonstrations
They also backed the introduction of English as an official language for the former French colony, results show.
Opposition parties say the changes transfer too much power to the president and had called for a boycott.
But supporters say the constitutional changes are essential for the Indian Ocean island's future development.
The government says it wants to attract more Anglophone investors and must therefore ensure that all legislation on investment is written in English.
Currently, France is the leading foreign investor in Madagascar, followed by Mauritius and China.
Mr Ravalomanana, a wealthy businessman, won a second five-year term after taking 54.8% of the vote in elections in December 2006.
The amendments give him authority to make laws directly if he declares a state of emergency.
When he claimed victory in presidential elections in December 2001 a bitter struggle for power ensued.
He used huge street demonstrations and military force to defeat former President Didier Ratsiraka, who had ruled for 23 years.