The move by the government-backed National Constituent Assembly on Tuesday paves the way for Guaido's prosecution and possibly his arrest.
It is unclear whether Maduro will actively threaten Guaido, who has embarked on an international campaign to topple the president's socialist administration. Maduro has avoided throwing the 35-year-old in jail to date.
"If the regime dares to kidnap me and carry out a coup, we will respond forcefully," Guaido said on Twitter after the decision.
"I do not have to respond to an organ that does not exist."
Tuesday's vote was unanimous. Constituent Assembly president and socialist party boss Diosdado Cabello accused the Guaido and the opposition of inviting a foreign invasion and inciting a civil war.
In January, Guaido declared himself Venezuela's interim president and vowed to overthrow Maduro. The US and roughly 50 other nations have recognised Guaido as Venezuela's legitimate leader.
"They don't care about the deaths ... they don't have the slightest idea of what the consequences of war are for a country," Cabello said.
On Monday, Supreme Court Justice Maikel Moreno said Guaido should be prosecuted for violating a ban on leaving the country when he went on a tour of Latin American nations that back a change in Venezuela's government.
The opposition leader, who had immunity from prosecution as head of the National Assembly, is also accused by Maduro's government of inciting violence linked to street protests and receiving illicit funds from abroad.
Guaido dismissed the Maduro-stacked high court as illegitimate.
But the opposition leader has come under increasing pressure in recent weeks. Officials jailed his chief of staff, Roberto Marrero, accused of involvement in a "terrorist" scheme to overthrow the government, and barred Guaido from holding public office for 15 years for allegedly hiding or falsifying data in his sworn statement of assets.
Maduro blames Washington for trying to install a puppet government to seize Venezuela's vast oil reserves.
With DPA
