CARACAS (Reuters) - Venezuelan opposition leader Henrique Capriles on Friday was banned from holding political office for 15 years, a move that could galvanize protests against the leftist government and upend a presidential election in 2018.

Venezuelan opposition leader and Governor of Miranda state Henrique Capriles (C) holds a copy of the Venezuelan Constitution as he speaks during a news conference in Caracas, Venezuela, April 6, 2017. REUTERS/Carlos Garcia Rawlins

Capriles, a two-time presidential candidate and current governor of Miranda state, was seen as the opposition’s best hope to defeat President Nicolas Maduro.

The national comptroller banned him from office due to “administrative irregularities” including breaking contracting laws and improper management of donations from the British and Polish embassies, according to a copy of the ban.

The punishment deals a blow to the opposition after stepped-up protests this week and accusations that Maduro, the unpopular handpicked successor of the late Hugo Chavez, was leading the country to dictatorship and cracking down on dissent.

Capriles responded to the measure in a defiant speech to emotive supporters at a small Caracas sports arena, describing the measure as a desperate gambit of a decaying dictatorship.

“You can shove your disqualification where the sun doesn’t shine,” said Capriles, flanked by opposition leaders. “This is not one person’s struggle, this is not Capriles’ struggle. This is the Venezuelan people’s struggle.”

The decision would also likely fuel anger ahead of an opposition protest planned for Saturday after a string of violent marches, spurred by the Supreme Court assuming control of congress last week before an outcry forced it to retreat.

A young man died in violence around protests on Thursday.

Over the last few days, authorities have accused Capriles of fomenting violence and bloodshed by leading increasingly intense protests against Maduro.

Capriles’ punishment falls under a comptroller’s office measure known as “disqualification” that blocks politicians from holding office if they are deemed to have committed “irregularities” in managing state resources.

The comptroller’s office notification to Capriles said he had 15 working days to appeal the decision at that office or 180 days to ask for its annulment at the top court. Both are pro-government and unlikely to overturn the decision.

When asked about the donations mentioned in the ban, the British Embassy referred questions to the Foreign Office, which did not immediately respond to an email seeking comment. The Polish Embassy did not immediately respond.

The government says the comptroller’s investigations are part of its anticorruption efforts. Opposition leaders say it is an arbitrary mechanism that allows the ruling Socialist Party to sideline popular politicians without due process.

‘DON’T COME CRYING’

The decision to politically neutralize Capriles will likely stoke tensions in Venezuela, where more than 100 political prisoners are now being held, according to the opposition and rights groups.

A ban on Capriles - a sports-loving lawyer who has tried to shake the opposition’s reputation of elitism by focusing on grassroots efforts with poor Venezuelans - would mean the country’s two top opposition politicians are barred from taking on Maduro.

Fellow opposition leader Leopoldo Lopez, Venezuela’s best-known jailed politician, was himself barred from office in 2008, when he was the popular mayor of a Caracas district.

Lopez had been expected to challenge Chavez in the 2012 presidential election but was forced to hand the baton over to Capriles, who lost that vote and a second, much closer one against Maduro after Chavez’s death. Lopez was later jailed amid violent protests in 2014.

Maduro’s government says a U.S.-backed business elite is responsible for Venezuela’s economic downturn and that it is trying to foment a coup to impose right-wing rule under the guise of peaceful protests.

“Mr. Capriles, you’re trying to ignite the country,” Socialist Party official Freddy Bernal said during a government rally on Thursday. “You’re looking for deaths. Don’t then come like a sissy saying that you’re a political prisoner.”

DEATH, ARRESTS IN PROTESTS

Venezuelan authorities confirmed a 19-year-old man was killed on Thursday during demonstrations, the first death since the Supreme Court controversy blew up last week.

The public prosecutor said later on Friday it would charge police officer Rohenluis Mata with the death of Jairo Ortiz, who the interior minister said was not a protester.

Opposition leaders say Ortiz was shot as authorities tried to break up the protest in the hilly, low-income Carrizal area on the outskirts of Caracas.

Local media reported Ortiz was a university student planning to emigrate from Venezuela, like many in the middle class.

Venezuela’s oil-dependent economy is suffering a brutal recession that has millions of people skipping meals because of steep inflation and low salaries.

“We’re not only protesting Jairo’s assassination, we’re also protesting this coup, and we’re asking for the opening of a humanitarian channel,” said Carlos Arancibia, a 25-year-old writer demonstrating against Ortiz’ death in a small march on Friday.