Dutch Prime Minister Mark Rutte had a warning for those in Mrs May's Conservative party as well as the Labour opposition who argue that a better deal can still be done before Britain leaves in four months.
In a direct appeal to farmers, she said the industry "deserves better" than the existing Common Agricultural Policy (CAP) framework set out by the EU.
Trump indicated he wanted the PM to take another look at the deal.
"This is the deal that is on the table", she said.
The European Commission chief warned the United Kingdom parliament it should not count on any renegotiation ahead of Britain's departure in March, as European Union leaders on Sunday approved a landmark agreement on Britain's exit.
Insisting the agreement "delivered for the British people" by regaining control of laws, money and borders, she said it would be put to an MPs vote on 11 December.
And DUP leader Arlene Foster warned Sunday she is ready to collapse the government to block a deal that would see Northern Ireland treated differently than the rest of Britain.
Mr Corbyn said: "The Prime Minister says if we reject this deal, it will take us back to square one".
"I don't believe that, so far, this deal delivers on what the British people really voted for", he told Sky's Sophy Ridge show.
The European Court of Justice (ECJ) in Luxembourg ruled that the case was "inadmissible, because there are no expatriates who are personally affected [by the negotiations for the UK's withdrawal from the EU] for now".
Britain would be entering unchartered waters - and quite possibly new elections - if the deal fails a second time arround.
British Foreign Secretary Jeremy Hunt said Sunday that the United Kingdom faced "very big risks" if the deal was rejected, according to the Reuters news agency.
Other opposition parties, including the Scottish National Party and the Liberal Democrats, have also said they would vote against it.
"Nobody really even knows what it means, it's just a threat that's being used by the extreme Brexiteers, and unfortunately some others, to say you've got to accept a really bad deal, and we don't have to", she said.
Should that good faith not translate to signed agreements, the legal backstops in the current deal would limit the messiness of the divorce, but definitely not favor the U.K.in that it will have to stick to laws and regulations it has no power to change from outside the European Union.
The small Northern Irish party that props up Mrs May's Conservatives-led government has said it will vote against the draft Brexit deal.
The European Union has formally approved a divorce agreement with Britain, the first country ever to leave the 28-nation bloc.