Slovenian opposition leader Janez Janša has been acquitted in a case in which he stood accused of being an accessory to abuse of office and faced two years in jail, a decision he says did little to make up for years of harassment.

The acquittal came "after almost fifteen years of interrogations, trials, media smear campaigns, and theft of health and life, freedom and time," he told a crowd of supporters who gathered in front of the Celje Courthouse on 18 April for the delivery of the verdict.

Janša, the leader of the Democratic Party, and his supporters and political allies have been denouncing the case as a politically-motivated show trial. He has been arguing that the case should never have made it to court.

The case involved a 15,000 m2 property in the Trenta Valley in the Triglav National Park that Janša sold in 2005, when he served as prime minister, to a construction company to partly finance the purchase of a flat in Ljubljana.

The prosecution alleged that he sold the land at a price much higher than the property was worth, which made it easier for him to buy the Ljubljana flat from the same company. As a result, it alleged that the director of the company had abused his office and defrauded his own company, while Janša and another defendant aided him in the crime.

The presiding judge, Cvetka Posilovič, said the court could not accept beyond reasonable doubt the claim that the Trenta property was worth only €20,000 and had thus been substantially overpaid, an argument the defence had been making throughout the trial.

The court had also not been presented evidence that the chief defendant, former Imos director Branko Kastelic, knew how much the property was really worth, nor did it accept the claim that the property was not worth as much because nothing could be built there due to conservation restrictions.

Since allegations against Kastelic had not been proven beyond reasonable doubt, it is logical the co-defendants could not be convicted either.

The judge said the verdict was based solely on a careful and conscientious assessment of all the evidence presented in the public hearings, and had not been swayed by media reporting, allegations or rallies outside the court.

The verdict is not yet final and the prosecution has announced an appeal.

Criticism of justice system continues

Janša has been in prison twice before, once in Yugoslavia on trumped-up political charges, and once in 2014 after being found guilty of corruption in a mega defence deal with Finnish contractor Patria, a verdict that was quashed on appeal and subsequently became statute barred.

Since at least the Patria trial, he has been a fierce critic of the Slovenian judiciary, which he has described as biased and corrupt. He has a long history of lashing out against judges, prosecutors and journalists, and has been found guilty of defamation twice in recent years.

The acquittal, which caps a trial that lasted almost two and a half years, appears not to have changed his view of the judiciary.

"Justice delayed is justice denied, regardless of the outcome. That is why our fight is only just beginning," Janša told the crowd, which welcomed his acquittal with cheers.

He said "hundreds of people" were in court procedures who ought not have been. Those unjustifiably prosecuted included "half of colleagues from the last government."

Janša said they would continue to fight for justice for those who were wrongly prosecuted and for those who were not but should be, suggesting the justice system needed cleansing.

But he said things would not change until everyone used their vote as the most powerful weapon in democracy, urging people to cast their vote in the upcoming referendum on pension allowances for deserving artists.

"Use your vote or else you may be banned from doing so," he said in a reference to a call by the coalition for voters to boycott the referendum for which a quorum is required. He said Slovenia was just a step away from people being disenfranchised.