May is battling to win support for a Brexit deal which will define both the UK's departure from the bloc and her future as leader.
She told the Times on Saturday that while none of the possible alternatives is better than the current Brexit deal, she would prefer a model similar to that of Norway, which is not an EU member but is part of the European Economic Area.
The former home secretary said the alternative "seems plausible not just in terms of the country but in terms of where the MPs are", but conceded that "nobody knows if it can be done".
A Indian-origin Brexiteer MP has come under pressure over her suggestion that potential food shortages between borders could be used as leverage to secure a better deal from the European Union, ahead of a vote in the UK Parliament next week over PM May's Brexit deal.
Mrs May's future hangs in the balance, with a heavy defeat in Tuesday's Commons showdown likely to lead to fresh pressure on her leadership.
"When I say if this deal does not pass we would truly be in uncharted waters, I hope people understand that this is what I genuinely believe and fear could happen".
"I would say to the colleagues who are voting against the withdrawal agreement. anything could happen after that".
Eurosceptic former party leader Iain Duncan Smith cautioned against the PM and her Cabinet deciding to "brazen it out", saying such an approach would be a "disaster".
"I believe that if the response is, "we've lost but we will do this all over again", it will become a leadership issue".
Hilary Benn, chair of the committee, said the government had "refused to face up to the hard choices confronting us". It is widely expected she will lose and ministers are concerned that the scale of defeat would be such it could bring down her government.
She acknowledged Tuesday's vote was "going to be difficult", but was adamant Mrs May would remain as prime minister even if her government was defeated, insisting "she will see us through this".
This would be triggered under the terms of the Fixed Term Parliaments Act 2011.
On this UpFront Arena, we debate the extent of interference in that referendum and whether it could have affected the result.
Opposition parties, including Labor, the Liberal Democrats and the Scottish National Party, have said they can not support the deal.
"If we go into government straight away we would start negotiating straight away. If it meant holding things a bit longer to do it, of course", he told Sky News.
Elsewhere in the capital, the pro-EU Best for Britain and second referendum campaign the People's Vote will hold a rally featuring politicians including Lord Heseltine and celebrities such as actors Charles Dance and Jason Isaacs.