A Man Booker prize-winning novel exploring gay relationships in Thatcher-era Britain has sparked a row over morality and media independence in the Czech Republic, after it was condemned as “pornographic” when it aired on the country’s leading cultural radio station.

Liberal critics believe the controversy over transmission of an extract from Alan Hollinghurst’s The Line of Beauty is being whipped up by conservatives to muzzle broadcasters in a move they liken to events in Hungary, where the rightwing government of Viktor Orbán stands accused of curtailing press freedoms and reining in public media outlets.

They also believe it is being used as a pretext to force out Petr Fischer, the highly respected editor-in-chief of Radio Vltava, a highbrow outlet of the publicly funded Czech Radio, which produced the offending broadcast. Fischer’s defenders – who have started a petition to save his job – argue that the Czech Republic is an unlikely battleground for a struggle over sexual mores, given that it is home to reputedly one of Europe’s most secular populations where the fight for gay rights provokes relatively little controversy.

The explicit content of a 35-second excerpt from Hollinghurst’s acclaimed 2004 novel seemed to arouse little interest when it originally went out on Vltava last June in a two-hour programme devoted to water as a literary theme. However, criticism followed a repeat of the programme on 7 July, a Saturday, after a listener complained on Facebook that the item was inappropriate for her children.

Although no official complaint was received, the post – since deleted – triggered further denunciations from members of the Radio Council, a supervisory body appointed by the Czech parliament.

One member, Tomáš Kňourek, launched a fierce attack on Fischer and dismissed Hollinghurst as “a homosexual activist dressed as a writer” whose “obscenities indicate the level of social life in Great Britain, a country that is voluntarily flooded with the most repulsive form of Islam”.

Kňourek labelled the broadcast “pornographic” and asked: “What will be the next open artistic window? Paedophilia? Terror on children? Ritual murders?”

Hollinghurst isn't the problem, it's just a pretext. The problem is me and open-minded people like me Petr Fischer, Radio Vltava

The backlash prompted Czech Radio’s director general, René Zavoral, to convene an emergency management meeting, where he issued a written statement saying the programme broke Czech broadcasting law prohibiting offensive content between 6am and 10pm. His statement contradicted Czech Radio’s own legal advice, which stated baldly that the law had not been broken and that the station had not broadcast pornography.

Zavoral’s concession has fuelled fears that he is buckling to pressure from populist political forces represented by figures like Kňourek, who one Czech Radio insider said represented an “alt-right agenda”.

“He’s constantly complaining that the radio doesn’t represent enough so-called ‘alternative media’, by which he means Sputnik, [the Russian state outlet widely seen as Kremlin-controlled],” said one Czech Radio programme-maker, who requested anonymity. Kňourek did not respond to a request for comment.

Speculation is mounting, meanwhile, that the issue will prompt the departure of Fischer, who joined Vltava last December with a brief to halt and reverse falling audience figures. Despite being praised for producing spicier programmes and boosting listening figures, Fischer said he expects to leave when his contract expires next month and is said to have been privately accused by Zavoral of “disloyalty” over the Hollinghurst controversy.

“Hollinghurst isn’t the problem, it’s just a pretext,” said Fischer, 49, a former London-based journalist with the BBC’s now defunct Czech service. “The problem is me and open-minded people like me. We have used social media to raise Radio Vltava’s profile and become interconnected with liberal-minded people – and that’s what they don’t like.”

Jiří Hošna, a Czech Radio spokesman, dismissed speculation over Fischer’s departure as “rumours” and said the organisation rejected criticism that the broadcast was “pornographic”.

But he said it should not have gone out on a weekend morning “due to its clear erotic context”, calling it a “dramaturgical error”.

Jakub Jirsa, a philosophy lecturer at Prague’s Charles University and one of more than 120 leading Czech intellectuals to sign to a petition calling on Zavoral to keep Fischer in his job, compared the current climate to the state repression that followed the Soviet-led invasion of Czechoslovakia in 1968 to crush the liberal Prague spring, a process known as “normalisation”.

“A new era of normalisation is coming,” said Jirsa. “It will be an era where things will be in limbo and everything will be bland and colourless. There will be no difference between public and state control.”