Congressmen in Ecuador say President Rafael Correa's plans to replace parliament with an assembly run by his supporters is an attack on democracy.
Mr Correa has accused parliament of being inept
After an overnight debate, parliament said it would make international protests against Mr Correa's plans to dissolve it.
Mr Correa announced his plans after claiming victory in elections on Sunday for a new constituent assembly.
The assembly is due to meet later this month to draft a new constitution.
Although the officials results have not yet been announced, preliminary election results show Mr Correa's Alianza Pais party with a strong majority in the new assembly.
Mr Correa said on Monday that the vote was a mandate to dissolve the opposition-controlled Congress.
The head of the legislature, Jorge Cevallos, said the dissolution would be unconstitutional.
Mr Correa has accused the opposition-run Congress of corruption and inefficiency.
He said the proposed constitutional reforms would make Ecuador a more just society and tackle endemic political instability.
Critics say the reforms will focus more power in the president's hands and this will frighten off foreign investors.
The Constituent Assembly is due to start work on 31 October and is scheduled to last 180 days, with a possible extension of up to 60 days.
The draft constitution will then be put to a national referendum for approval.
The impoverished Andean nation has thrown out three presidents in the past 10 years, and successive governments have been roundly criticised.