Hungary’s prime minister-elect, Péter Magyar, has pledged to pursue those who “plundered, looted, betrayed, indebted and ruined” his country, promising “a new era” after a landslide election victory over his far-right predecessor Viktor Orbán.

Magyar, whose centre-right Tisza party won at least 138 of the 199 seats in parliament, said the full election results should be confirmed by 4 May and he hoped his government could be installed the next day.

“Our country has no time to waste,” he said during a wide-ranging press conference on Monday. “We will do everything in our power to ensure this truly marks the beginning of a new era … The Hungarian people didn’t vote for a simple change of government, but for a complete change of regime.”

Magyar, a former Orbán loyalist, secured a decisive two-thirds supermajority that should allow him to roll back laws that helped the outgoing nationalist prime minister transform Hungary into an “illiberal democracy” during his 16 years in power.

Orbán’s four successive governments have comprehensively eroded the rule of law in Hungary, packing the courts with judges loyal to him, turning 80% of the media into government mouthpieces and vastly enriching a coterie of cronies.

Orbán has battled repeatedly with the EU – which has blocked billions of euros in funds – over a range of policies including justice, migration and Ukraine. Both the US president, Donald Trump, and Russia’s Vladimir Putin backed him.

Magyar said his government would swiftly implement anti-corruption measures, restore the independence of the judiciary and ensure freedom of the media, in hopes of a rapid unfreezing of EU cash. “I hope … we can prepare an agreement,” he said.

He said Hungary would “never again be a country without consequences”, promising to establish a national asset recovery office that would ensure the “political and economic criminals” who “stole from the country” would be held responsible.

Alongside other reforms aimed at unlocking the €17bn in EU funds, he said Hungary would join the European public prosecutor’s office, giving EU investigators powers to probe fraud cases and examine how the bloc’s money was used under Orbán’s rule.

The new government would “fundamentally … do everything to restore the rule of law, plural democracy, and the system of checks and balances”, Magyar said, but insisted it would “not use anti-democratic measures to restore the rule of law”.

It would, however, “amend the constitution, and write into it that in future anyone can only serve as prime minister for two terms – which is eight years”, he said. Applied retroactively, this would bar Orbán from running again.

Magyar also said one of the new government’s first steps would be to “stop state-funded propaganda” by suspending news broadcasts from “state-captured” public TV and radio until unbiased coverage could be ensured by a new supervisory board.

Describing them as “puppets” of the former regime, Magyar called on the heads of the country’s two highest courts, audit office and competition and media authorities, as well as the chief prosecutor and Hungary’s president, to resign.

“He was appointed just to sign everything,” the prime minister-elect said of the president, Tamás Sulyok. “We don’t need people like that. To me, he is not the president. I call on him to leave. If he doesn’t, we will find a solution.”

EU leaders reacted enthusiastically to his victory on Monday. Although he outlined policies – particularly on migration and Ukraine’s accession to the EU – likely to cause friction with the bloc, Germany’s chancellor, Friedrich Merz, called it “a good day” that had sent “a very clear signal against rightwing populism”.

Merz said decision-making in the EU, long hampered by Orbán’s repeated vetos, should get easier. The German government spokesperson in Berlin said a change of government in Budapest should lead “very quickly” to the release of EU cash for Ukraine.

Orbán, who last visited Moscow in November, blocked a €90bn loan to Ukraine after accusing it of sabotaging Russian oil deliveries to his country, something Kyiv has repeatedly denied. He delayed – and often opposed – EU sanctions on Russia.

Ursula von der Leyen, the European commission president, said Brussels would start work with the new Hungarian government “as soon as possible” to make progress on issues including the release of frozen European funds.

Von der Leyen reiterated her warm welcome to Magyar’s victory, saying “today Europe is Hungarian without any question” and that “the people of Hungary have spoken and they have reclaimed their European path”.

Both the Slovak and Czech prime ministers, Robert Fico and Andrej Babiš, close political allies of Orbán, congratulated Magyar on his win and said they were looking forward to “constructive cooperation” with the new government.

But the Patriots for Europe group in the European parliament, home to Fidesz and other far-right parties such as France’s National Rally (RN), the Dutch Freedom party (PVV) and Italy’s Lega, said the result was “a setback” for “forces advocating … for democratic self-determination and traditional European values” within the EU.