BUDAPEST - Tens of thousands protested against the government of Viktor Orban in downtown Budapest on Saturday, led by a lawyer once close to the administration but who recently launched a political movement that aims to challenge the prime minister.

Protesters marched to Parliament in the unusually warm spring weather, some of them shouting "we are not scared" and "Orban resign!"

Many protestors wore the red-white-green national colours or carried the national flag, symbols that Mr Orban's party used as its own for the past two decades.

"These are the national colours of Hungary, not the government's," said 24-year-old Lejla, who travelled to Budapest from Sopron, a town on the country's western border.

The march was led by Mr Peter Magyar, 43 - who used to be married to Mr Orban's former justice minister Judit Varga - and who eventually plans to launch his own party.

Three protesters at the march said Mr Magyar appealed to them because he had been close to the Orban government and has an inside knowledge of how it works.

"We had known that there is corruption, but he says it as an insider and confirmed it for us," said Ms Zsuzsanna Szigeti, a 46-year-old healthcare worker wearing a Hungarian flag that covered her entire body.

She said she was concerned about the education and the healthcare systems, and worried about corruption. "I trust that there will be a change," she said.

Mr Magyar became widely known in February when he delivered incendiary comments about the inner workings of the government. He accused Mr Antal Rogan, the minister who leads Mr Orban's office, of running a centralised propaganda machine.

He also published a recording of a conversation with his former wife where Ms Varga detailed an attempt by a senior aide to Mr Orban's cabinet chief to interfere in a graft case. Prosecutors are now investigating the statements.

The probe comes at a politically sensitive time for Mr Orban ahead of European parliamentary elections in June, and follows a sex abuse scandal that brought down two of his key political allies - the former president and Ms Varga - in February.

According to data by pollster Median, published by news weekly HVG in mid-March, 68 per cent of voters have heard of Mr Magyar's entry into the political field and 13 per cent of them said they were likely to support his party. REUTERS