The National Union of Journalists has warned that the proposed privatisation of Channel 4 would “irreparably damage” Scotland’s news media.

The body is just the latest to ring alarm bells about the future of the broadcaster north of the border if it were to be sold off.

As the Herald on Sunday revealed last week some of the biggest movers and shakers in Glasgow’s flourishing TV and film industry believe they face “catastrophic” consequences if the channel goes private.

However, there are also wider concerns about Scottish media diversity and quality if, as many fear, commercial pressures jeopardise news, current affairs and investigative documentary-making.

Nick McGowan-Lowe, organiser at the NUJ’s Scottish Office, said: “Scotland is best served by a vibrant and varied news media, and the plan to privatise Channel 4 will irreparably damage that.

“In 2020 alone it spent £19m in Scotland, but privatisation means that money will vanish from supporting media jobs and the creative industries and instead go straight into the bulging pockets of shareholders.

“The only result will be a poorer deal for Scots viewers who currently benefit from strong news coverage and innovative programming.”

Conservative ministers insist they have not yet made their minds up about Channel 4. They have previously said the broadcaster, which, though state owned, fully funds its programming through advertising, may need an injection of private capital to compete with streaming giants like Netflix.

They also say that they would keep some of the unique characteristics of the channel. Industry experts have questioned this logic. They say the Channel 4 model as it stands would not be appealing to bigger broadcasters, such as ITV or Channel 5 owners Viacom. So either it would sell for little - or buyers would want to chance its nature, Glasgow is Scotland TV town. It is home to broadcasters ST V and BBC Scotland. Its council led a campaign to bring a Channel 4 hub to the city. That effort pulled together much of the Scottish screen sector. Now the same alliance is fighting to keep the channel in state hands.

Late last month city leader Susan Aitken wrote to three ministers warning them that their Levelling-Up agenda was being endangered by talk of privatisation. Her letter was signed by leading industry figures Jane Rogerson and Ross Harper of Red Sky Productions, Alan Clements of Two Rivers Media, and Jane Muirhead of Raise The Roof Productions.

The campaign is staying out of party politics. “While we would prefer Channel 4 to remain publicly owned, our opposition to privatisation is not ideological,” Ms Aitken and the TV executives said in their letters. “Were it genuinely possible to sell Channel 4 but retain its unique publisher broadcaster status together with its existing (perhaps enhanced) obligations to work with and commission from independent producers outside of London, and in the UK’s nations and regions, the likely damage to our creative economy could be avoided.”

Some Conservatives are worried too. The Herald last week reported that Jamie Greene MSP, a former TV executive, felt “nervousness and trepidation” about the privatisation. He has no ideological objection, but he wants to ensure Channel 4 continues to do what it does.

Mr Greene said: “Channel 4 gives a voice to people who struggled to have a voice, whether that’s marginalised groups, the LGBT, disabled or BAME communities or whether it’s ensuring they have really wide range of voices from right across the UK, in all four nations.

“Channel 4 really prides itself on is is speaking to and about every part of the UK and surely that is what lies at the essence of the government’s levelling up and makes a case for the Union?”

Channel 4 has another unique feature. It is the only major channel which broadcasts the same output across these islands - it also serves the Republic of Ireland.

Those opposing privatisation say they are trying to "speak Tory”, to convince London Conservatives using their own arguments.

Ms Rogerson, a former BBC journalist, stressed the Britishness of the channel.

“Channel 4 doesn't have specific Scottish channels or slots like BBC Scotland or STV for ITV. It has only one news offering. What you see on channel 4 in Truro is what you see on channel 4 in Lerwick,” she said. That's a powerful responsibility to reflect all of the diverse voices and lives of each part of the UK back to the whole UK. A privatised channel 4 is in danger of losing that responsibility rather than strengthening it - which is what the UK Government should be focussing on. Campaigners say the mooted sale - which is far from finalised - jeopardises a unique business model which sees Channel 4 commission shows, but let makers keep intellectual property rights. This “publisher broadcaster” role of Channel 4 - combined with a commitment to buy programmes outside London - is a key pillar of the Scottish screen sector.

The SNP’s John Nicolson MP, a former prominent TV journalist for BBC and ITV, has been harrying Culture Minister Nadine Harries over their decision-making, He says he believes the danger is that some Conservatives just ‘hate’ the channel.

Glasgow campaigners did not bother contracting Ms Dorries after it emerged in questioning at a Westminster committee that she, wrongly, thought the broadcaster was subsidised by the taxpayer. They have deliberately targeted ministers with responsibility for Levelling Up instead.

Her department, nevertheless, issued a statement last week.

“We value Channel 4’s contribution to levelling up and are clear its public service broadcasting remit and the government’s commitment to independent regional productions would continue following any potential sale,” it said.

“There is a wealth of evidence on the future challenges for linear TV broadcasters and it is right that a change in ownership to support Channel 4’s long-term sustainability is considered. This could allow more and quicker investment in creative content and new platforms to support the wider creative industries.”