The global NGO Open Society Foundations (OSF) confirmed on Thursday that it was considering closing its Budapest office, following a years-long campaign against the OSF founder George Soros in Hungary.

OSF chief and former US ambassador Patrick Gaspard personally traveled to Budapest to inform the local staff, according to Austria's Die Presse. The OSF now reportedly aims to open a new office in Berlin during the summer of 2018. The Hungarian news web site 444.hu said the OSF office would close by the end of August.

The OSF later told DW that closing the branch was one option it was considering, but that a move would most likely take place if the Stop-Soros Act came into force in its current form.

"We are in the process of thinking, of planning, weighing our options," OSF spokesman Csaba Csontos told Reuters in Budapest. "The government has committed to passing the Stop Soros law... It will be a symbolic step which serves to stifle non-government groups."

"At this moment we need to think about how that might affect us who support them, and how we might proceed," he said

Hungarian-born US billionaire George Soros established the OSF in the early 1990s with the aim of promoting democracies in formerly communist states of eastern Europe. However, the organization has faced intense pressure in Hungary after right-wing nationalist Viktor Orban took power in 2010. Orban and his allies have portrayed Soros as a powerful and sinister figure intent on undermining the power of the state and reversing Orban's strict anti-migrant policies.

Read more: Orban launches a personal battle with Soros over Hungary

Many western observers condemned the campaign, accusing Orban and his allies of using the 87-year-old Soros as a scapegoat. Others have argued that the campaign against Soros, who is Jewish and a Holocaust survivor, was anti-Semitic. The government has repeatedly shrugged off such criticism.

The Hungarian prime minister is currently pushing a legislation dubbed the "Stop Soros" plan to crack down on NGOs and their foreign founders. Late last year, a ruling party politician posted a photo of a dead pig with Soros' name on it.

Read more: War of words between Soros and ruling Fidesz heats up

Paper publishes list of Soros 'mercenaries'

Soros has also faced increased pressure from right-wingers in other parts of the world, including UK and the US, for his support of liberal policies and opposition to Brexit.

The campaign in Hungary escalated last week when a pro-government newspaper Figyelo published the list of what it dubbed Soros "mercenaries" in the country. The 200-strong list includes academics, NGO employees, journalists and politicians. Many of the people listed teach at another Budapest-based project funded by George Soros, the Central European University.

Hungary's government has also threatened to force CEU out of the country. According to Die Presse, authorities in the Austrian city of Vienna pledged a space that CEU could use as a back-up campus in case it needs to leave Hungary.