Hungary's first independent radio station, Klubrádió, which was forced off the airwaves in February, said on Sunday that its former frequency had been allocated to a station owned by a group close to Prime Minister Viktor Orbán.
Klubrádió, whose news and discussions are often critical of the government, has been streaming online since a court upheld a decision by media authorities not to extend its broadcasting licence.
The liberal-leaning commercial station was one of the only remaining opposition radio voices in Hungary.
The news marked yet another setback for the independent media in the country, which has been under pressure since Prime Minister Viktor Orban's return to power in 2010.
Hungary’s media council (NMHH), controlled by the ruling Fidesz party, in September cited alleged violations of the country’s media law for the decision to not renew Klubrádió’s licence past February 14 and put the frequency up for tender.
The European Commission and the United States denounced the move as a new attack on press freedom in Hungary.
On March 30, the NMHH awarded the 92.9 FM frequency to Spirit FM, which belongs to a media group close to Orban.
Head of Klubrádió, Andras Arato, alleged the regulatory body has acted illegally by "granting the frequency to a media group close to the government even though we have launched legal proceedings, which are still ongoing, to get the frequency back," he told AFP on Sunday.
He told Euronews in February that he planned to appeal to Hungary's highest court, the Curia.
Spirit FM's owner, the ATV group, "tries to maintain a semblance of independence but any opposition voice on its channels is strictly controlled," Arato said.
NMHH has said its decision is not political.
In a February statement, the National Associated of Hungarian Journalists called Klubrádió "the only remaining public service broadcaster in Hungary whose content is not under government influence".
The European Union's executive previously urged the government in Hungary to allow the liberal-leaning radio station to continue broadcasting.
During an online press conference of the European Commission, spokesman Christian Wigand confirmed the executive had sent a letter to Hungary's permanent representation in Brussels expressing its concerns over the move.
Wigand said the station’s loss of its broadcasting frequency had occurred “on the basis of highly questionable legal grounds”, and that Hungary “should respect the EU’s charter of fundamental rights, including the rights to freedom of expression, information and the freedom to conduct a business”.
Hungary is currently ranked 89th out of 180 countries in the Reporters Without Borders (RSF) press freedom index. It was 23rd when Orban returned to power in 2010.