Speaking alongside May in Strasbourg on Monday, Juncker warned if the deal was voted down, there would be "no third chance".
Jon Snow, the anchor of Channel 4 News, posted a tweet on Tuesday morning saying a "lawyer contact" told him "the Attorney General said NO last night to the validity of Mrs May's "new European Union deal".he been told to go away and find a way to say YES".
May's deal was defeated 391 to 242 on Tuesday evening and will be followed on Wednesday by a debate and vote in the House of Commons on the prospect of the United Kingdom leaving the European Union with "no deal" in place - which MPs are also expected to reject.
In a written legal opinion, Cox said the United Kingdom could still not extract itself from the terms of the divorce deal unilaterally, a key demand of pro-Brexit British politicians.
"It is hard to see what more we can do", the statement said, adding that the latest vote "significantly increased" the likelihood of a no-deal Brexit.
The defeat came after May and European Commission President Jean-Claude Juncker announced changes Monday created to overcome lawmakers' concerns about provisions created to ensure the border between EU member Ireland and Britain's Northern Ireland remains open after Brexit.
"It's likely the pound will react in light of the aftermath of tonight's vote - but in which way depends on the outcome of the vote".
The government was even weighing up whether to scrap Tuesday's planned vote on the basis that no significant changes had been secured.
If the deal does not pass, MPs will be granted a vote on Wednesday on whether to proceed to a no-deal Brexit on 29 March and another on Thursday on whether to extend article 50.
"The Prime Minister and I have agreed on a joint legally binding instrument relating to the Withdrawal Agreement".
She claims the changes now means the Irish backstop - the insurance policy created to avoid a hard border in Ireland - could not "become permanent".
Sky News reports that not all of the DUP MPs are "on the same page" in regard to how the party will vote on Tuesday evening's meaningful vote.
The European Commission president insisted there would be no further negotiations on the issue. Afterward, hard-core Brexit supporters in May's Conservative Party and the prime minister's allies in Northern Ireland's Democratic Unionist Party both said they could not support the deal.
And anti-Brexit campaigners haven't abandoned the idea of a new referendum on remaining in the EU. "Let us be crystal clear about the choice - it is this deal or Brexit might not happen at all".
The two sides have also published a "joint statement" which commits to replacing the backstop with "alternative arrangements" by the end of December 2020.