Video report by ITV News UK Editor Lucy Manning
Ed Miliband has been given support from David Cameron and Nick Clegg over his decision to take on the Daily Mail in response to an article he claimed "besmirched" his father.
In a bitter row with the national newspaper, the Labour leader said it was a lie to assert that Marxist academic Ralph Miliband "hated Britain" and had left an "evil legacy".
The Daily Mail said it stood by "every word" of its essay on Mr Miliband's father, who came to Britain as a Jewish refugee and served in the Royal Navy during the Second World War before becoming a proponent of what the newspaper called "one of the world's most poisonous political doctrines".
Mr Miliband was given the right to reply after the offending article was published on Saturday, but his defence of his father was accompanied by the reprinted essay and a leader column explaining why the paper was standing its ground.
Prime Minister David Cameron said he would "react in exactly the same way as [Ed Miliband]" if his father was attacked in print.
Deputy Prime Minister Nick Clegg wrote on Twitter:
I support @ed_miliband defending his dad. Politics should be about playing the ball, not the man, certainly not the man's family.
Former deputy prime minister John Prescott told ITV News: "Do bear in mind [Ed Miliband's] father fled from Europe to fight the fascists, joined the Royal Navy, and at that time Viscount Rothermere - who owned the Daily Mail - was actually writing in support of the fascist Blackshirts.
A Daily Mail spokesman said:
– Daily Mail spokesman
We ask fair-minded people to read our editorial today. For what this episode confirms is that you cannot allow politicians anywhere near regulating the press.
While we respect Mr Miliband's right to defend his father - and he has done so in the Daily Mail today - it is worth stressing that Ralph Miliband wasn't an ordinary private individual but a prominent academic and author who devoted his life to promoting a Marxist dogma which caused so much misery in the world.
He hated such British institutions as the Queen, the Church and the Army, and wanted a workers' revolution. Our readers have a right to know that.
Ed Miliband, the Labour leader, is the leading advocate of statutory controls of the press in Britain under which politicians could ultimately decide what appears in newspapers.
His father - to whom he constantly refers in his speeches - was a proponent of one of the world's most poisonous political doctrines under which freedom of expression was crushed and newspapers controlled by governments.