The assurances are expected to be delivered in an exchange of letters on the eve of next Tuesday's vote - but the European Union has not so far found a form of words which would provide the game changing boost needed by May to win the vote. Previously, it had been expected that the government would have 21 days to come up with a fresh plan to put before the Commons.
A cross-party group of MPs sought Tuesday to amend a finance law to limit the government's tax-raising powers in the event of "no deal", as a way of forcing it to stop such a scenario.
The motion means that should the Prime Minister lose the meaningful vote on Tuesday, she will have to come back before MPs and explain her next steps within three days.
Brexit-backing Tories accused Mr Bercow of flouting Commons procedures by allowing a vote on the proposal, tabled by former attorney general Dominic Grieve.
Mr Bercow said he had made an "honest judgement" in the interests of MPs.
The Speaker, who insisted he was "trying to do the right thing and make the right judgements", was heckled by Tory MPs as he told Mr Francois the answer to his question was simple.
"If that is a choice then I say let's go on WTO rules".
Work and Pensions Secretary Amber Rudd said history will take "a dim view" of the PM's Cabinet if it presses ahead with a no-deal Brexit if MPs vote against her agreement next week.
The Commons amendment, tabled by Labour's Yvette Cooper, is created to limit the Treasury's ability to spend money on no-deal preparations, without the explicit consent of Parliament.
The future of Brexit remains deeply uncertain - with options ranging from a disorderly exit from the European Union to another membership referendum - because British lawmakers are expected on January 15 to vote down the deal May struck with the EU in November.
"I think he stepped way over the mark out today he's broken with parliamentary precedent".
"It seems clear that May will lose the vote, the only real question is how much does she lose by", Usherwood added.
Mr Grieve said his amendment was an attempt to "accelerate the process" if the vote was lost so as to avoid the prospects of a no-deal Brexit.
The reports emerged as Theresa May faces an uphill struggle to get her Brexit deal approved by the Commons. "Obviously she has had a lot of important discussions over the Christmas break with other European leaders and I'm sure she would want to update parliament".
70% of Tory MPs believe that the UK would be able to quickly strike trade deals with the likes of the United States and China, and 58% of them are confident that such new trade deals would more than compensate for any lost European Union trade.
Commons Leader Andrea Leadsom noted there were "some concerns" about Mr Bercow's decision and asked him to confirm that he acted with "full advice" from the Commons clerk and other parliamentary advisers. "That is why we are taking every opportunity possible in parliament to prevent no deal", Corbyn said, cited by the Guardian.