Budapest (AFP) - Hungarian NGOs have long felt the heat under strongman Prime Minister Viktor Orban -- but they now fear that, emboldened by Donald Trump's victory, the right-wing premier will turn the screws even tighter.

First in line may be groups backed by Hungarian-born billionaire financier George Soros, whose foundation once funded the Oxford studies of a young Orban more than 25 years ago.

Last week the deputy head of Orban's ruling party Fidesz, in power since 2010, said that non-governmental organisations should be "cleaned out of here".

Szilard Nemeth said that criticism of government policies by "fake" civil organisations set up to "influence politics" by Soros and others was "impermissible".

The remarks triggered alarm among beleaguered NGOs, many of which -- in the absence of a credible political opposition -- have long attacked Orban's sweeping revamp of state institutions and hardline anti-immigration stance.

"This is a new level of NGO-bashing," said Marta Pardavi, co-head of the Hungarian branch of the Helsinki Committee, a human rights group that provides free advice to asylum-seekers.

Nemeth name-checked the body as potential targets along with civil rights group TASZ and corruption watchdog Transparency International.

"The notion that we should be swept away like rubbish or have no right to comment on politics shows their arrogant intolerance of different views," Pardavi told AFP.

Her office, staffed by some two dozen lawyers, heaves with case files as well as reports that have slammed Orban's anti-migration policies.

She freely admits that her organisation relies on foreign funding to continue operating. But "otherwise it's not possible to do human rights advocacy work in Hungary," she says.

Mirroring pressure in Russia under President Vladimir Putin, scrutiny of foreign-funded NGOs has been cranked up since Orban was re-elected in 2014.

Dozens of groups supported by Norway were investigated by government auditors over alleged financial irregularities.

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None were found, and the purge prompted US President Barack Obama to warn Hungary against a "clampdown" on civil society.

- 'Foreign money' -

Orban's spokesman Zoltan Kovacs told AFP that the election of Trump as US president -- Orban is a great admirer -- will bring in a "new era".

"With the new US administration, pseudo civil sector activity is not going to drive international politics," he told AFP.

But Kovacs stressed that Hungary was not about to kick anybody out.

"The rule of law prevails in Hungary. It's impossible to have singular or targeted action against anyone. Any new rules will apply to all and be in line with EU and international law," Kovacs said.

But he added: "It's clear we need changes, we don't know how much foreign money or foreign influence there is behind NGOs."

"Many on the political left claim they are civilians but they clearly have political goals and act like the political opposition."

A draft bill addressing "transparency" of NGO funding will be submitted to parliament around April, according to a schedule on the Hungarian parliament website.

Details have yet to be worked out though, said Kovacs.

- Soros in crosshairs -

The 86-year-old Soros, whose Open Society Foundations (OSF) body has funded civil groups in Eastern Europe since the 1980s, is in the crosshairs of the new push.

"Soros has decided that he will be Viktor Orban's opponent and opposition in Hungarian politics... People have the right to know which organisations he's doing this through," Orban's chief-of-staff Janos Lazar said last week.

Hungarian officials have even accused Soros-backed NGOs of posing a national security risk during Europe's migration crisis by allegedly colluding with human-smugglers and "terrorists".

It's a charge Marta Pardavi says could scare off small donors if they fear their data might be compromised.

"What a wonderful way of discrediting NGOs," she said.

The OSF meanwhile has no plans to quit Hungary, its president Christopher Stone said.

"We are not the opposition, neither in Hungary, nor elsewhere. We are promoters of open debate," he said in a statement emailed to AFP.

The body says it currently funds over 60 Hungarian NGOs, ranging from corruption watchdogs and investigative journalists to human rights and anti-discrimination bodies.

It has also awarded thousands of scholarships to Hungarian students -- including Orban in 1989 -- while the Hungarian Helsinki Committee and TASZ were even praised by Fidesz before 2010.