Iain Duncan Smith says Lord Heseltine is 'from the past'
Former cabinet minister Iain Duncan Smith has dismissed Lord Heseltine as a "voice from the past" after the Tory grandee's attack on Boris Johnson.
Mr Duncan Smith, who like Mr Johnson is campaigning to leave the EU, criticised "name-calling", calling it "childish".
It comes after Lord Heseltine said Mr Johnson's "judgement is going" after his comments about Hitler and the EU.
The ex-deputy PM also said he would be "very surprised" if Mr Johnson went on to become prime minister.
The UK's EU referendum takes place on June 23. The government is officially campaigning for a vote to remain in, but several high profile Conservatives are backing the Leave campaign, with Mr Johnson one of its figureheads.
On Sunday Mr Johnson, the former London mayor, compared the EU's aims in creating a "single authority" in Europe with Napoleon's and Hitler's.
Remain campaigners have rounded on him, and the European Council president said his comments were "absurd".
But Mr Johnson has stood by his remarks and on Wednesday described the criticism he has received as "synthetic outrage".
Lord Heseltine's intervention on Tuesday, in which he said the "preposterous, obscene" remarks had "crossed the bounds of domestic debate", provoked a strong reaction from Mr Duncan Smith, who quit the government in March over cuts to disability benefits.
"It's always good to hear voices from the past. I would be grateful if they remained in the past," he told the BBC.
"My simple comment is: cut the name calling because this is childish and the public is fed up with it.
"All of you in the past who were once responsible for these actions, the best you can do is say let's engage with the debate and stop calling people names, because I think that demeans us and I don't think politicians should do that."
Another Leave campaigner, Tory backbencher Jacob Rees-Mogg, described Lord Heseltine - a longtime EU enthusiast whose challenge helped trigger Margaret Thatcher's departure from Downing Street - as "a frightful old humbug who divided the Conservative Party more than anybody else in our modern history".
Mr Duncan Smith also told the BBC key elements of the government's agenda had been "parked or dropped" in this Queen's Speech, because David Cameron was keen to avoid any debate or argument which touched on Europe.