The European Council president sought to make clear that the deal is the “only possible one”, amid speculation that Ms May could try to either renegotiate the package or that parliament might seek a Norway-style status instead.
It comes after the Bank of England and the Treasury released data suggesting a no-deal scenario could lead to a savage recession in the UK, with a devastating impact on household incomes.
Speaking from the G20 summit in Argentina, Mr Tusk pointed out that the deal struck between the European Union and the UK represented an “orderly divorce”.
He went on: “A few days before the vote in the House of Commons, it is becoming more and more clear that this deal is the best possible – in fact the only possible one.
“If this deal is rejected in the Commons we are left with, as was already stressed a few weeks ago by Prime Minister May, an alternative – no deal or no Brexit at all.
“I want to reassure you that the EU is prepared for every scenario.”
Speculation over how many Tory MPs could oppose Ms May’s deal has been rife in recent days, with some suggesting it could be as high as 100.
But a Press Association analysis indicated that only 18 Tory MPs have publicly said they will specifically vote against the deal, including ex-cabinet ministers Owen Paterson, Theresa Villiers and Priti Patel.
A further 42 Tory MPs have said they will not vote in favour of the deal – but this does not mean they will necessarily vote against, or that they intend to vote at all.
This category includes the likes of Esther McVey, who resigned from the cabinet on 15 November saying “I cannot vote for this deal”, and Suella Braverman, who resigned from the government on the same day saying she was “unable to sincerely support the deal”.
Another 23 Tory MPs have said publicly they are unhappy with the deal or they may have difficulty supporting it.
If every opposition MP voted against her deal, and they were joined by the 18 Tory MPs who have said they will also oppose it, this alone would be enough to defeat the deal.
The Bank of England has warned the UK economy could go into meltdown, with a collapse in house values, a slide in the strength of the pound, surging inflation and soaring interest rates if Britain leaves the EU without a Brexit deal.
In a worst-case scenario, it said a chaotic Brexit could trigger the worst economic turmoil since the Second World War, dwarfing the financial crisis of 2007-08.
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