The IMF is set to intervene in the increasingly bitter Brexit battle after the Bank of England's warning withdrawal could cause recession provoked a furious backlash from the Leave campaign.
IMF managing director Christine Lagarde was expected to deliver a sharp, downbeat, warning regarding the economic impact of Britain turning its back on Brussels as she was meeting Chancellor George Osborne at the Treasury.
And in a double-whammy attack against the Leave side, Tory former prime minister Sir John Major was accusing the Brexit campaign of "fuelling prejudice" with dangerous falsehoods on immigration.
In a strongly worded apparent swipe at senior Conservatives in the anti-EU camp, like Boris Johnson and Michael Gove, Sir John insisted "a boundary had been crossed" and fear-inducing rhetoric risked provoking long-term divisions in the country.
"As the Leave arguments implode one by one, some of the Brexit leaders morph into Ukip, and turn to their default position - immigration. This is their trump card. I urge them to take care, this is dangerous territory that - if handled carelessly - can open up long-term divisions in our society.
"Of course, it is legitimate to raise the issue of the sheer number of those wishing to enter our country. I wholly accept that. Nor do I wish to silence debate. We mustn't overlook genuine concerns, but these should be expressed with care, honesty and balance. Not in a manner that can raise fears or fuel prejudice. The Leave campaign are crossing that boundary, and I caution them not to do so.
"We must not let emotions be stirred by false fear - nor allow that false fear to impair our judgment on the future of our country," Sir John said at Oxford University in his most high profile intervention in the referendum campaign so far.
The hard-hitting attack came as Bank of England governor Mark Carney's warning that Brexit could trigger a technical recession provoked demands for his sacking from prominent Leave campaigner, and Tory MP member of the Commons Treasury select committee, Jacob Rees-Mogg.
"Mark Carney has intervened speculatively in a political matter. It's the responsibility of the Monetary Policy Committee to be independent, and he's decided to make a deeply political choice in a referendum which is the concern of the British people, and therefore, he should be fired," the MP told Sky News.
Mr Rees-Mogg accused the governor of deliberately talking down sterling for political reasons.
"It is quite extraordinary, and I think unprecedented, for a governor of a central bank to tell people to short his own currency," he said.
Prime Minister David Cameron, who was accused of dodging a head-to-head TV debate on Brexit, insisted it was the Bank's job to warn of risks to security after it said withdrawal could "materially" hit UK growth and cause the pound to fall "sharply" and inflation to spike, while the economy would suffer as households and businesses reined in spending.
The French economy minister, Michel Sapin told BBC Newsnight that Brexit would boost the far right across Europe.
"In all of our countries we've seen an increase in popularism and the extreme right. We all believe that if the UK leaves these forces of the extreme right will become stronger and it will be the same thing in all our countries and yours.
"In France, in Germany, in Italy, in Spain, there will be demands for their own votes. You can imagine what would happen then, we'd have a sort of fragmentation of Europe which would have its own consequences for the UK in turn because the UK has a strong interest in Europe, a Europe where trade and people can move around easily.
"Can you imagine how that would work and look if each European country turned into itself and shut its borders, going back 50, 100 years into the past? You can imagine that would be extremely damaging for the United Kingdom and its population.
"If we do have Brexit, and the UK leaves the EU then there will be serious economic consequences both for the UK and Europe in general. I think if the UK leaves it will create huge uncertainty for us and the UK and that will have a significant effect which can only be negative for the UK economy," he said.
Cabinet heavyweight and leading anti-EU campaigner Mr Gove insisted he has no interest in becoming deputy prime minister in a post-Brexit vote deal to try to heal Tory wounds.
"No. I don't want to be Nick Clegg part two. Love him as I do," the Justice Secretary told The House magazine.
Labour leader Jeremy Corbyn was launching a voter registration drive in Liverpool as he urged young people to "take control" of the campaign.