Next week, the EU's leaders will meet at a summit to discuss the extension of Britain's membership after 29 March, as well as the terms and length of the delay. That left Britain facing a disruptive "no-deal" exit from the bloc on March 29, when a two-year countdown to the country's departure runs out. But Mrs May's party is still severely split, with more than half voting against the delay.
The backstop is "an insurance policy that would only be used if we are unable to agree a sufficiently ambitious future relationship between the EU and the United Kingdom that would remove any need for it", Mr Donohoe said in a speech at Bloomberg's European headquarters in London on Friday.
The Cheshire MP, who resigned as Work and Pensions Secretary over the deal four months ago, said Leaver MPs will "have to think a different way" when the Prime Minister's European Union divorce returns to the Commons next week.
However, the difficulties of negotiating the divorce deal without opening up negotiations on future trading terms have led to problems over European Union insistence on a "backstop" insurance policy for the border that has caused British lawmakers to refuse to ratify the deal. But the failure of everyone else to come up with anything close to an alternative plan means that her deal remains the most likely outcome.
"She didn't want there to be an extension and brought forward the withdrawal agreement twice".
The UK Government would have to take further steps to stop that happening.
Her authority hit an all-time low this week after a series of parliamentary defeats and rebellions.
The focus has moved to how long Brexit could be pushed back for if the deal falls.
The Prime Minister apparently breaking her word by attempting to Article 50 - she will require the EU's agreement to do so - will leave many wondering whether they can trust her other promises; for example her vow to stand aside as party leader before the next general election, made in exchange for Tory MPs not backing her ouster in a recent vote of no confidence.
Still, Mrs May has an arduous task ahead.
The Prime Minister has said the delay only be until June if Parliament passes her deal - or a much longer one if they reject it a third time.
Professor Marc Stears, director of the Sydney Policy Lab at the University of Sydney and former chief speechwriter to Britain's Labour Party, said: "Mrs May's position ought to be very weak".