The so-called National Assembly, which has been declared illegitimate by Maduro’s government, approved a statute extending its term into 2021 on Saturday.
The move paved the way for Western-backed Guaido to remain the “president in charge” of the defunct assembly.
“In the face of unconstitutional claims to self-proclaim term extensions that are not warranted, we trust that the justice system will do its job with an iron fist,” Maduro said in televised address on Monday.
Dozens of opposition lawmakers are facing criminal investigation for crimes such as treason.
The move to extend the assembly came despite a parliamentary vote that gave Maduro’s ruling socialist party 91 percent of the seats in Congress earlier this month.
Some opposition parties had boycotted the congressional elections. But over 100 political parties and associations took part in the polls. The Congress is now scheduled to be sworn in on January 5.
Speaking to the new lawmakers last week, Maduro said the elected parliament must define the criminal and administrative responsibility of members of the former National Assembly.
He said that the work of the previous National Assembly had been “a failure, a rollback” and that the new parliament must present the people of Venezuela with information on all crimes committed by former deputies.