Péter Magyar, once an insider in the ruling Fidesz party, declares that ‘Change has started in Hungary which can’t be stopped, Ednews reports via The Guardian.

Tens of thousands of Hungarians protested against the country’s leadership on Saturday in one of the biggest demonstrations in years, organised by a former government insider who has shaken up Hungary’s political landscape.

Péter Magyar, a lawyer and former diplomat who used to belong to an elite circle around Hungary’s ruling party, publicly broke with the government in February and is now aiming to challenge the position of Viktor Orbán, the powerful prime minister.

Over the past 14 years, critics have accused Orbán of increasingly undermining democratic institutions, cosying up to Moscow and Beijing and overseeing a corrupt patronage network.

The longtime Hungarian leader, who began his career as an anti-communist liberal, has moved his Fidesz party to the right. He served as prime minister between 1998 and 2002, but since returning to power in 2010, he has taken a more nationalist, il­liberal path, frequently clashing with the EU.

Now, Magyar – who was previously married to Hungary’s former justice minister – is trying to build a new kind of opposition movement. On Saturday afternoon, young people, pensioners and families with children marched through central Budapest and tried to squeeze into the vast square in front of the parliament, with parts of the crowd spilling over to nearby streets.

Some carried signs bearing the names of their hometowns. Many waved Hungarian flags.

“From now, nothing will be as it’s been,” Magyar said as he made the case for a European-facing and meritocratic Hungary. “Change has started, which can’t be stopped,” he declared.

Addressing the demonstrators, Magyar accused the country’s media and the prosecutor’s office of lacking real independence, laid out allegations of high-level government corruption, and said he would launch a party that would run in the European parliament election in June.

“We, Hungarians, are coming together,” he told the crowd, calling for rightwing, leftwing and liberal Hungarians to respect one another and work together to replace the current political elite.

Protesters who spoke to the Observer said they found Magyar – who had pitched himself as a centrist figure and had criticised both the government and parts of the opposition – convincing.

István, a middle-aged man who had travelled to Budapest from western Hungary, said it was his first anti-government protest. “I think the opposition has been helpless,” he said as he marched toward parliament.

“I find him credible,” he said of Magyar, adding: “He was a beneficiary of the system, he gave it up and turned his back on it – and that shows something.”

Magyar’s decision to publicly challenge the government came as Hungary’s president, Katalin Novák, resigned after it emerged that she had pardoned a man convicted of helping cover up a sexual abuse case at a children’s home.

Some demonstrators cited the case as part of the reason for their own growing political participation.

Kitti, a young woman who said she began attending protests after the pardon controversy, said there was a feeling that the traditional opposition “is not really motivated to change this regime”.