Ecuadorean President Rafael Correa on Monday condemned as a "shameless deal" the top court's ruling to reinstate 50 fired opposition lawmakers.
His comments, broadcast by Ecuadorean TV, stopped short of rejecting the ruling. Correa is at loggerheads with Congress as he tries to wrestle power from the country's old elites.
"They [the judges] struck a shameless deal with the 57 dismissed lawmakers," Correa said.
The Constitutional Tribunal voted 6-3 to return the legislators to their jobs, said Tarquino Orellana, vice president of the court.
"This opinion is problematic because it is rushed, completely irregular because it goes against regulatory procedures," said Orellana, who opposed the measure.
The Supreme Election Tribunal, which originally fired the lawmakers, rejected the Constitutional Tribunal's ruling and threatened to sue the judges.
The ruling, approved by six of the nine court members, comes as lawmakers were scheduled to decide on a bill to dissolve the court.
On March 6, legislators fearing for their jobs should the constitution be rewritten, sacked the head of the Supreme Election Tribunal in an attempt to foil the referendum.
However, the following day, the Supreme Election Tribunal ordered the removal of the legislators who had stood in its way.
Ecuadoreans last week massively backed Correa's call for a new body that could strip powers from congressmen, seen as enjoying too many vested interests in state companies and the judiciary.
The 50 lawmakers reinstated on Monday had been among 57 forced out last month by an electoral court, which said they violated election law by trying to block the referendum.
A spokesman for the court had earlier said all 57 were reinstated but changed that to 50 after reviewing the court documents.