The amendments, which increase powers to question and remove ministers and withdraw confidence in the Cabinet, emerged from a national dialogue King Hamad bin Isa Al-Khalifa organized last year after an uprising.
The main opposition party Wefaq withdrew from the dialogue, saying it did not go far enough to offer real reform.
The king, in a televised speech Sunday said: "Our people have proven their desire for continuing with reforms ... We complete the march today with those who have an honest patriotic desire for more progress and reform.
"I must mention here that democracy is not just constitutional and legislative rules, it is a culture and practice and adhering by the law and respecting international human rights principles," he said.
"I beseech all sectors of society to work together so that all their sons adhere to the law..."
The changes outlined by the king also limit some royal authority.
The king would have to issue more explanations on the selection process for the Shoura Council, the 40-member upper house of Parliament that is appointed by the monarch. The king also would need wider discussions with political and judicial leaders before any decision to dissolve the elected Parliament and call new elections.
"This reflects a denial of the demands for better representation for Bahrainis and a fair judiciary," said Wefaq official Matar Matar, noting the reforms could have been effected via legislation rather than constitutional changes. "It ignores previous promises from the crown prince on a government that represents the people."
