As reported by Reuters, the UK's Labour opposition party will be demanding that the UK's parliament will have the final say in any Brexit deals, including the power to send ministers back for more negotiations instead of an outright exit without a deal in place.
Theresa May reached a transitional period agreement with leaders from the European Union last week, and now the real hard work has to begin: reaching a long-term trading agreement between the two powers post-Brexit. Whatever shape the final deal takes remains to be seen, but the UK's parliament has been informed that it will be a take-it-or-leave-it deal. As the Labour party's Brexit policy chief strategist, Keir Starmer, will be pointing out in a speech later, “If Parliament rejects the prime minister’s deal, that cannot give license to her – or the extreme Brexiteers in her party – to allow the UK to crash out without an agreement. That would be the worst of all possible worlds."
Reuters went on to note that, "a so-called ‘No Deal’ exit would be likely to cause upheaval on financial markets, throw cross-border trade into confusion, and spark a political crisis in the world’s sixth largest economy. Labour will seek to give parliament more options — including a return to Brussels for fresh talks — by amending the legislation that will formally end Britain’s EU membership on March 29, 2019."