The row over the Daily Mail’s attack on Ed Miliband’s father intensified this week when a leading campaigner against antisemitism accused the paper of an anti-Jewish slur.

In a tweet on Wednesday, John Mann, the chairman of the All-Party Parliamentary Group Against Antisemitism, called the article on the late Ralph Miliband a “classical age-old antisemitic smear about disloyal Jews”.

His intervention followed an already heated controversy over the feature in the paper on Saturday, which had branded Ralph Miliband as “the man who hated Britain”.

In an outraged riposte published in the Mail two days later, Ed Miliband said that his father had loved Britain because it had saved him from the Nazis.

Ralph Miliband, a Marxist academic who died in 1994, arrived in Britain as a refugee from Nazi-occupied Belgium when he was 16 and served in the Royal Navy during the war.

It's a classical age-old antisemitic smear about disloyal Jews - John Mann

Rabbi Danny Rich, chief executive of Liberal Judaism, said that the newspaper was “playing with fire. The danger is that the paper’s attack on Ralph Miliband gives legitimacy to those that seek to cast all refugees and immigrants as ‘outsiders’ and question their loyalty. This is a concern not only for Jews but all those that share our experience and with whom we must stand.”

Leading Labour thinker Lord Glasman denounced the article as “a classic McCarthyite slur”, recalling that American McCarthyism in the 1950s had been “overwhelmingly and predominantly anti-Jewish”.

Ralph Miliband had never been a Communist Party member, he noted, but had been part of a strongly anti-fascist milieu and a “long tradition of Jews wanting to make the world better”.

David Hirsh, editor of the website Engage, which counters antisemitism, said that some of the online reaction to the article had “fed off the idea of antisemitism”.

But Rabbi Alan Plancey, a Conservative councillor in Elstree, Hertfordshire, saw nothing antisemitic in the article. “The Daily Mail are having a go at Mr Miliband and this is nothing to do with him being Jewish. The word isn’t mentioned and I don’t think we should start digging it up and making it into something it isn’t… This is a battle against Labour. The Daily Mail is a Conservative paper, so it’s political.”

Conservative MP Lee Scott commented: “Any tone of xenophobia or prejudice didn’t come across to me in the original article, but I was looking at it from a political angle.”

But he sympathised with Ed Miliband’s reaction and said he would be “quite upset if someone had a go at my father who was no longer alive”.

Former Labour MP Eric Moonman said: “I don’t think for a moment that it’s antisemitism. I must admit, like most Jews, I see dangers everywhere, but I don’t see it in this case.”

A souce at the Mail said: “This was purely about politics and Ed Miliband’s anti-freemarket views — such as his threats against energy companies, grabbing land from housebuilders and raising taxes against big corporations. The article sought to trace the origins of Ed Miliband’s views and that led back to Ralph Miliband.

“We find any suggestion of antisemitism in what is a purely political debate to be absolutely spurious.”

Both the author of the article, Geoffrey Levy, and the paper’s deputy editor, Jon Steafel, are Jewish.

Neither the Board of Deputies or Jewish Leadership Council would comment.