Theresa May is hoping to secure enough votes to back the Brady Amendment in order to seek alternative arrangements for the Irish backstop - which has been the number one sticking point in getting a Brexit deal so far - and bring the notion to Brussels that the only way that parliament will approve of the withdrawal agreement is that changes be made to the backstop.
Macron called on May to present the EU's chief negotiator Michel Barnier with her next steps for avoiding a no-deal Brexit on March 29, which he said "no-one wants, but. we must all, despite everything, prepare for".
In her final message before the Commons showdown began, the PM admitted she must attempt to renegotiate the Withdrawal Agreement, and appealed for MPs to vote for an amendment that would give her a "mandate" to demand the Irish border backstop is replaced.
Brexit hardliners from May's Conservative Party are set against the divorce deal due to its so-called backstop proposal, which could see Britain indefinitely tied to European Union trade rules in order to keep open the border with the Republic of Ireland.
Despite a last minute gamble aimed at buying off rebels in her Conservative Party, the prime minister will face a knife-edge battle to block a proposal that would hand the parliament the power to delay the process and prevent a no-deal divorce.
The Withdrawal Agreement May struck in November with the EU says the United Kingdom will remain in a customs union "unless and until" "alternative arrangements" are found to avoid a hard border.
The other amendment which could drastically alter Brexit has been tabled by Labour MP Yvette Cooper.
In an effort to appease those Tories who are proposing to back Boles and Cooper's plan to delay Brexit, May promised they would have another chance to vote to stop Britain leaving the bloc without a deal, according to people in the room Monday.
Her spokesman said her strategy had won the backing of her cabinet but it is not a foregone conclusion that lawmakers will back the amendment, one of seven proposed to try to break the impasse.
Another faction, led by both Conservative pro-EU and pro-Brexit lawmakers, are trying to craft a plan to return to Brussels with two new options.
Mr Corbyn's call for more time to be given for MPs to consider alternatives to the Brexit deal was the first in a series of amendments being put to the vote on Tuesday evening.
"I think we should send the Prime Minister back to Brussels with a strong mandate to be able to say if you compromise with us on this one issue, on the backstop, we would be able to a get an agreement - an agreement that is nearly there", he told BBC Radio 4's Today programme.
British stocks jumped Tuesday and the pound was firmer ahead of the votes.
Opposition to the backstop by pro-Brexit lawmakers - who fear it will trap Britain in regulatory lockstep with the European Union - helped sink Mrs May's deal earlier this month.
But the European Union was "standing tough" on its position of no renegotiation and they were "mesmerised" with what was happening in Parliament, BBC Europe editor Katya Adler said.
The amendment proposed by Conservative MP Dame Caroline Spelman and Labour MP Jack Dromey, which rejects the United Kingdom leaving the European Union with no deal, was passed in Parliament on Tuesday.
But EU leaders insist they will not change the legally binding Brexit withdrawal agreement.
"While we have been working closely with our suppliers on contingency plans it is not possible to mitigate all the risks to our supply chains and we fear significant disruption in the short term as a result if there is no Brexit deal".
Ireland's European Affairs Minister, Helen McEntee, said: "There can be no change to the backstop".