The Romanian government has defended plans to quash hundreds of corruption cases, including the conviction of the leader of the ruling party for vote-rigging, despite EU concern over how the holder of the bloc’s presidency is tackling graft.

During two years in power, the Social Democrats (PSD) have forced the dismissal of Romania’s top anti-corruption prosecutor, sought to decriminalise some graft offences and launched an overhaul of the judiciary that critics warn will boost political control over the courts.

The moves have already sparked Romania’s biggest protests in decades, but now the government is seeking an amnesty for some offenders and wants to issue a special decree to annul verdicts issued by the country’s supreme court since 2014.

Minister for justice Tudorel Toader drew up the emergency decree in the wake of the Romanian constitutional court’s decision that one of the five judges on the country’s supreme court was not appointed properly in 2014.

The government argues that all the court’s subsequent decisions are invalid, opening the way for hundreds of corruption cases to be retried and fuelling fresh fears for the rule of law in Romania just weeks into its first six-month presidency of the EU.

PSD leader Liviu Dragnea could expect to have his 2015 suspended sentence for vote-rigging quashed, and for his appeal against an abuse of office conviction to be delayed. His criminal record currently prevents him from serving as prime minister, but he effectively runs premier Viorica Dancila’s government from the wings.

“In no other country is the supreme court formed in violation of the law,” Mr Toader told a committee of the European Parliament on Wednesday.

“Through this appeal for annulment [of verdicts] we do not want anyone to escape punishment, but you cannot tell a Romanian that he was tried illegally but has to remain in prison.”

‘Prove innocence’

Ms Dancila told Romanian television that she supports the emergency decree, which she claimed would “in no way prevent the fight against corruption” and would allow those who had been convicted “to prove their innocence”.

“All these people who have suffered deserve a fair trial . . . It’s sad that people went to prison. Their families and health were destroyed,” added Ms Dancila, a close ally of Mr Dragnea who took office after the PSD ousted two previous premiers who challenged his authority.

Romanian president Klaus Iohannis, a sharp critic of the government, called the decree “crudely unconstitutional”.

“It shows that, in fact, the PSD does not care about Romania – the PSD cares about its own politicians with criminal problems and seeks solutions for them.”

In Brussels, meanwhile, European Commission spokesman Margaritis Schinas said: “It is essential for Romania to get back on track in the fight against corruption to ensure an independent judiciary and to avoid any further step back.”

Jyrki Katainen, a vice-president of the European Commission, was more blunt.

“Unbelievable news!! Romanian people deserve rule of law,” he tweeted of the emergency decree.

“The whole EU is based on liberal-democratic values, including the rule of law. Several member states, including Poland, Hungary and Romania, seem to be deviating from the sustainable, liberal-democratic path. In my opinion, this is the biggest challenge the EU is facing at the moment,” he added.

Romanian opposition parties and civil society groups said they would call protesters back onto the streets if the government passed the emergency decree. Some 450 people were injured when riot police launched a violent crackdown on demonstrators in Bucharest last August.