Former Mayor of London Boris Johnson has said the UK faces a "triple whammy of woe" if it remains in the EU, while stating Leave has won the "democratic argument".
That will include facing a £20bn blackhole in EU finances, an extra £2.4bn bill from Brussels and liability for future eurozone bailouts.
However, Remain's Chuka Umunna said the extra bill claim is "nonsense", while Britain Stronger in Europe's Will Straw said the future bailouts statement had "no basis" in fact.
The former London mayor's comments come a day after former Prime Minister John Major said that the Leave campaign were focusing on immigration as it had lost the economic argument.
"The risks of Remain are massive. Not only do we hand over more than £350m a week to the EU, but if we vote to stay the British people will be on the hook for even more cash," Johnson said.
"It is a triple whammy of woe: The eurozone is being strangled by stagnation, unemployment and a lack of growth, it could explode at any time and we will be forced to bail it out.
"The botched bureaucratic response to the migration crisis means the Eurocrats are demanding even more of our money. And now we find that there is £20bn billion black hole in the EU's finances."
Meanwhile, Prime Minister David Cameron is likely to upset a few more Tories today as he appears next to former foes to make the case for Remain.
Cameron will make a speech alongside Tim Farron, the Lib Dem leader, Harriet Harman, the former Labour leader and Natalie Bennett, the Green Party leader, after having unveiled a dossier today.
With just two weeks to go until the referendum, the quartet will accuse the Leave campaign of being "reckless and undemocratic" for failing to provide a plan for the UK after the referendum.
Trade unions are also out in force, though not standing with the Prime Minister. The general secretaries of 10 trade unions said that Brexit would mean the Conservatives "negotiate away our rights".
The trade unions' comments echo the sentiment of Labour leader Jeremy Corbyn and shadow chancellor John McDonnell, who have warned of a "Tory Brexit". While some Labour politicians will share the stage with Cameron et al, Labour's front men will not.
The comments come as a new YouGov poll shows a four point lead for Leave, which garnered 45 per cent of support, compared to 41 per cent who back Remain. Some 14 per cent were undecided.
A TNS poll also found that Leave was on 43 per cent, with Remain on 41 per cent. The pound weakened on the news.