The editor of the Scotsman has accused Alex Salmond of being ill-informed and ignorant after the former Scottish first minister described the newspaper as being irrelevant.

Salmond, who has joined an activist investor seeking to make him chair of the Scotsman’s parent company, Johnston Press, had been quoted as saying that “for the first time in its 200-year history the Scotsman has become largely irrelevant”.

Frank O’Donnell, who became editor of the paper in April, said he could not allow the former SNP leader’s “ill-informed attack” to go unchallenged.

“For those who missed it, Mr Salmond said the title is now ‘largely irrelevant’ and that he would restore pride and confidence through a ‘pro-Scottish’ agenda,” wrote O’Donnell in a Scotsman article headlined Protecting independence paramount.

“Mr Salmond is either ignorant of the paper’s content or perhaps he equates ‘pro-Scottish’ as being pro-SNP.”

Salmond has teamed up with Christen Ager-Hanssen to replace the chair and chief executive respectively of Johnston Press and set a new strategic direction. Ager-Hanssen is the largest shareholder in the publisher, which owns titles including the Yorkshire Post and the national title i.

Salmond said if the boardroom coup was successful he would not seek to have editorial control of the Scotsman, which opposed Scottish independence, but that he would like it to become more pro-Scotland.

“The idea of Mr Salmond being chairman of Johnston Press and restricting his involvement to prosaic monthly business meetings seems highly unlikely,” O’Donnell wrote.

“It has long been known that nationalist supporters in Scotland have coveted a quality daily newspaper that supports the yes movement and have looked at buying the Scotsman to further their agenda.”

In the 2014 independence referendum, the Scotsman backed a no vote. However, O’Donnell has since said the title, which has a daily circulation of about 21,000 and about 120,000 daily unique browsers on its website, will take a neutral stance on independence and party politics.

Ager-Hanssen, who owns the Swedish version of the free-sheet Metro, told BBC Radio Scotland’s Good Morning Scotland programme it was wrong to suggest Salmond would meddle with the editorial stance of the paper.

“What a chief executive in a company like this in a group do, they appoint editors and editors decide what to write,” he said, adding that O’Donnell was “totally wrong – it’s as simple as that”.

Commenting on Salmond, whose first job was selling copies of the Edinburgh Evening News, a Johnston Press stablemate, Ager-Hanssen said: “We share the same mission, Johnston Press is a 250-year-old company, it is a Scottish company, I want to take it back as a champion for Scotland.

“My mother told me about the Scotsman newspaper way back in the 80s when I was living in Stavanger, and how impressive that newspaper was. I want to take it back to that glory days. And I share the same mission with Alex.”

At around the turn of the millennium, circulation of the Scotsman peaked with sales of more than 100,000 a day.

Johnston Press bought Scotsman Publications – the parent company of the Scotsman, Scotland on Sunday, Edinburgh Evening News and Herald & Post newspapers – for £160m in 2006.