Venezuela's pro-government constitutional assembly has stripped three of the country's most influential opposition parties of the right to participate in next year's presidential election.

The Constituent Assembly ruled that parties who boycotted this month's local elections had lost legitimacy, requiring them to reapply for legal status and potentially eliminating them from the 2018 presidential race.

The decree has infuriated Venezuela's opposition and drew criticism from the United States, whose embassy said: "The Venezuelan government and its illegitimate Constituent Assembly are inventing rules as they go along. This is not democracy."

Richard Lapper, an expert on Latin American politics and economics at Chatham House, said the move was emblematic of Venezuela's growing authoritarianism.

"Although you can criticise the opposition for the way they've handled everything, this is a clear sign the government is closing down the democratic space," he told The Independent. "It has been expected that this would be the next step."

He said NGOs were "now talking about Venezuela as a complex humanitarian emergency" as the government is not allowing any assistance into the country, which is suffering widespread shortages of basic goods. "The shortages are really beginning to bite in the most dramatic fashion," he added.

"If there's no means of changing the government within the democratic system, then clearly he [President Nicolas Maduro] is going to control the democratic system in the same way as the North Koreans."

Opposition protesters clash with security forces in Venezuela

The Justice First, Democratic Action and Popular Will parties did not run candidates in this month's mayoral polls in protest against what they said was a biased election system designed to perpetuate the leftist president's "dictatorship."

The government-stacked National Electoral Council relocated dozens of voting centres in predominantly opposition strongholds days before those votes. In one state, opposition members presented evidence that electronic ballot tabulations did not match up with printed copies held by observers.

Ruling socialist party candidates won 18 of 23 governorships in a surprise victory for a government that has struggled to combat rising crime, malnutrition and medicine shortages.

Mr Maduro had warned that could cost them participation in future votes and the Constituent Assembly echoed that position on Wednesday, saying the parties had lost their legal status and should re-apply to the National Election Board.

"A party that has not participated today cannot participate anymore," Mr Maduro said after casting his ballot in the December election. "They will disappear from the political map."

Given that the board is pro-Maduro and authorities are constantly throwing up obstacles to the opposition, that could well mean those parties are now effectively unable to run in the presidential election due before the end of 2018.

A turbulent year in Venezuela Show all 11 1 /11 A turbulent year in Venezuela A turbulent year in Venezuela Demonstrators scuffle with security forces during an opposition rally in Caracas, Venezuela, April 4, 2017. Venezuelan security forces quelled masked protesters with tear gas, water cannons and pepper spray in Caracas after blocking an opposition rally against socialist President Nicolas Maduro. The clashes began after authorities closed subway stations, set up checkpoints and cordoned off a square where opponents had planned their latest protest against the government and the crippling economic crisis. Carlos Garcia Rawlins: "For me that was the day that made a difference, never before had I seen the protesters and police clashing men-to-men and struggling back and forward. From then, the strategy of the police changed and they never faced the protesters so close again." Reuters A turbulent year in Venezuela A man who was set on fire by people accusing him of stealing during a rally against Venezuela's President Nicolas Maduro runs amidst opposition supporters in Caracas, Venezuela, May 20, 2017. Marco Bello: "I spotted a man running in front of me as a group of protesters, most of them hooded and with makeshift shields, were chasing him so I followed them. Some 100 meters down the street, the protesters caught the man and surrounded him. When I walked up and went through the circle of people to take pictures, someone had already poured gasoline over the man and set him on fire. Reuters A turbulent year in Venezuela "Rowdy groups of government supporters busted into Venezuela's opposition-controlled National Assembly. There were several clashes happening at the same time, so I tried to follow a small group of attackers as they pushed their way through the main building. By the time I got into the building, they had already finished hitting people and were on their way out, leaving behind an opposition lawmaker covered in blood. I quickly went over to the politician, Leonardo Regnault, whose grey suit was spattered in blood. He was up against an ornate wooden door, clearly in a state of shock. Another opposition lawmaker, Luis Stefanelli, was standing next to him, hands up in a sign of surrender and pleading with the attackers to stop the beating. Reuters A turbulent year in Venezuela A member of the riot security forces points a gun through the fence of an air force base at David Jose Vallenilla, who was fatally injured during clashes at a rally against Venezuelan President Nicolas Maduro's government in Caracas, Venezuela, Reuters A turbulent year in Venezuela A demonstrators attends a rally against Venezuela's President Nicolas Maduro's government in Caracas, Venezuela, June 19, 2017. Ivan Alvarado: "I was under the highway photographing some protestors who had surrounded a woman they accused of stealing a phone from someone. I turned around to check what was happening behind me and saw this man appearing from the shadows to see what was going on. The white on his face is salt, which the protestors said helped to reduce the effects of the tear gas." REUTERS A turbulent year in Venezuela Riot security forces clash with demonstrators as a motorcycle is set on fire during a protest against Venezuelan President Nicolas Maduro's government in San Cristobal, Venezuela, May 29, 2017. Carlos Eduardo Ramirez: "Security forces arrived to disperse demonstrators that already had burned two taxis and a bus, throwing tear gas and pellets and the demonstrators' response was to throw molotov cocktails and one of those petrol bombs reached a National Guard member, setting him and the motorbike on fire." Reuters A turbulent year in Venezuela Riot security forces detain a demonstrator during a rally against Venezuela's President Nicolas Maduro's government in Caracas, Venezuela, July 28, 2017. Rock-throwing Venezuelans braved tear gas and rainstorms, blocking streets in protest against a legislative super-body to be elected two days later that critics call an attempt by President Nicolas Maduro to create a dictatorship. Carlos Garcia Rawlins: "After many hours of very violent clashes between the demonstrators and security forces, the National Guard in an attempt to end the situation, suddenly advanced their line very quickly, even going beyond where I and other photographers were taking cover. All the protesters who did not react fast enough to leave the place were detained." Reuters A turbulent year in Venezuela Opposition lawmaker Carlos Paparoni is hit by jets of water during riots at a march to the state ombudsman's office in Caracas, Venezuela, May 29, 2017. A group of young Venezuelan lawmakers has risen to prominence on the violent front line of anti-government marches that have shaken the South American country for three months, bringing 75 deaths. On the streets daily leading demonstrators, pushing at security barricades and sometimes picking up teargas canisters to hurl back at police and soldiers, the energetic National Assembly members are heroes to many opposition supporters. Carlos Garcia Rawlins: "I remember clearly how instants after I spotted Paparoni standing in front of 'The Whale', the common name of the water cannon armoured cars, he was flying through the air due to the unstoppable power of the water, as if he was a feather. Fellow protesters had to drag him out of the place, because from where I was, he seemed to have been unconscious." Reuters A turbulent year in Venezuela Flames erupt as clashes break out while the Constituent Assembly election is being carried out in Caracas, Venezuela, July 30, 2017. Deadly protests rocked Venezuela as opposition voters boycotted an election for a constitutional super-body that unpopular leftist President Nicolas Maduro vowed would begin a 'new era of combat' in the crisis-stricken nation. Carlos Garcia Rawlins: "Suddenly, a bomb exploded in the capital during an opposition protest and wounded seven police officers in what seemed to be the spread of more aggressive tactics. We were taking photos from close by but the police panicked and chased everyone away, firing teargas, rubber bullets and pellets." Reuters A turbulent year in Venezuela An injured opposition supporter is helped by volunteer members of a primary care response team during clashes with riot security forces at a rally against Venezuelan President Nicolas Maduro's government in Caracas, Venezuela, June 22, 2017. Ivan Alvarado: "This image was taken next to an airforce base where another protestor was fatally injured that day. I don't know how this man was injured, I first saw him as the first aid volunteers carried him out from the midst of the tear gas. You can really see the pain in his expression as he cries out. After I took the image the motorbike speeded off down the highway." Reuters A turbulent year in Venezuela A demonstrator shouts slogans in front of police officers during a women's march to protest against President Nicolas Maduro's government in Caracas, Venezuela Reuters

Mr Maduro, 55, is expected to run for re-election despite the disastrous state of the economy in Venezuela, where millions are skipping meals and struggling to survive amid one of the world's highest inflation rates.

Two of his potentially biggest rivals already cannot run against him: Popular Will leader Leopoldo Lopez is under house arrest, while Justice First leader Henrique Capriles is prohibited from holding political office.

"We alert the world and all democratic governments that banning opposition political parties is yet another measure by the dictatorship that deserves rejection and condemnation," said Mr Capriles' party colleague, Tomas Guanipa.

Mr Maduro and his allies say the Constituent Assembly has brought peace to the OPEC nation after months of opposition protests earlier this year in which more than 125 people were killed.

Demonstrators said they were fighting for freedom, but the government condemned them as violent subversives.