Britain, France, Spain and Germany were among 15 European nations to officially recognise Juan Guaido as Venezuela's "interim president", in move which was swiftly denounced by Nicolas Maduro as a "gringo plot to overthrow the revolution".
"The imposition of any solutions or the attempt to legitimize the attempt of the power usurpation is, in our viewpoint, the direct and indirect interference in Venezuela's internal affairs".
Already recognised by the United States, Canada, Australia and several Latin American countries, Guaido is trying to force the socialist leader from power so he can set up a transitional government and hold new elections.
The 35-year-old Guaido, head of the country's National Assembly, has breathed new life into a previously fractured and tired opposition. A senior air force general recognized Guaido as president on February 2.
Italy does not recognize the result of Venezuela's presidential election last May, which Maduro won, and wants new elections as soon as possible, Italy's foreign minister told Agence France-Presse on Monday.
Venezuela has the largest reserves in the world, but production has plunged under Mr Maduro's tenure.
British Foreign Secretary Jeremy Hunt promptly followed suit, saying on Twitter he hoped "this takes us closer to ending humanitarian crisis".
Spain has strong links to Venezuela historically, culturally and economically, meaning their government's endorsement of Guaido will be a significant blow to Maduro.
Here is a summary of whom key players are backing, after Guaido declared himself acting president on January 23 in defiance of the leftist Maduro.
But the socialist leader showed no signs of caving in and lashed out at the European Union and the Trump administration, which has also put pressure on the Venezuelan government by imposing sanctions on Venezuelan oil exports and demanding Maduro's departure. Maduro told Italian television Sunday.
The socialist leader said the move would leave the White House "stained with blood", accusing the USA president of trying to stage a coup.
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Maduro has offered to call parliamentary elections; however, Le Drian insisted that only a presidential election could end the crisis "because it's a presidential regime" in Venezuela.
Mrs May yesterday called for an immediate end to Maduro's regime, which has led to crippling food and water shortages and hyperinflation of 1.3million per cent.
Before the closed-door meeting got under way, Prime Minister Justin Trudeau condemned a "dictatorship willing to use force and fear" to maintain its power.
Canada has announced a humanitarian relief package for Venezuela.
"As a country that has an open-arms policy towards Venezuelans, we have received many important figures from the democratic opposition", said Federico Hoyos, Colombia's ambassador to Canada.
Trump warned that military intervention remains "an option" for dealing with the crisis in Venezuela.
Tens of thousands of Venezuelans have turned out in recent protests to demand Maduro's exit, although he appears to have the support of the nation's powerful military and security services.
On Monday, Guaido said the European Union needed "to act in unison so that the forces, who are still supporting Maduro feel all the weight of Europe's diplomatic and political pressure".
Maduro, for his part, stood defiant, accusing the United States of preparing a coup in the South American country and rejecting a US -backed effort to send emergency food and medicine into his country.
Mr Guaido, who leads the National Assembly, declared himself caretaker leader last month in a move splitting worldwide powers and bringing Venezuelans onto the streets.