Saying a rejection of the Brexit deal would be a catastrophic and unforgivable breach of trust, May urged the parliament to "forget the games and do what is right for our country".
Mrs May is facing a heavy defeat on Tuesday as Conservative backbenchers prepare to unite with Labour to vote the deal down.
However, his priority is to force a national election and he said he would propose a vote of confidence in the government "soon" if May loses on Tuesday.
Mr Blackford said that revoking Article 50, which sets a deadline of 29 March for the date of departure, and holding another referendum would be the most sensible option for moving forward.
"What is more likely if this deal is rejected is that we have the risk of Brexit paralysis and when that happens no one knows what might happen and the big risk, and what people worry about, is that we don't actually deliver what people voted for", Jeremy Hunt told Sky News on Friday.
In a warning to Conservative rebels ahead of the vote, Brexit Secretary Stephen Barclay said that Brexiteers seeking "ideological purity" are in danger of seeing Britain not leave the European Union at all.
May has urged Parliament to support her little-loved European Union divorce deal so that Britain doesn't leave the European Union on March 29 without an agreement on exit terms.
Theresa May told lawmakers they should not let down Brexit-backers.
Corbyn said: "I think parliament did vote for an amendment to the Finance Bill this week, which indicated its opposition to no deal, but it isn't totally specific on it".
If a confidence vote failed, he'd be under pressure to back a second Brexit referendum, risking a backlash from the many Labour supporters who voted to leave the EU.
"When you turned out to vote in the referendum, you did so because you wanted your voice to be heard".
Vince Cable, leader of the pro-EU Liberal Democrats, said parliament would act to prevent a no deal Brexit, and could ultimately seek to prevent Brexit altogether.
'Some of you put your trust in the political process for the first time in decades.
Meanwhile, London mayor Sadiq Khan has written in the Observer suggesting that Mrs May should step down and call a general election if she loses next week's vote.
"I would love a general election because that would allow us to give a very clear statement to the Tory government as to where we're standing", he said.
But he has insisted the United Kingdom should not afraid of a no-deal Brexit, despite forecasts from the Treasury and Bank of England warning that it could trigger an economic crisis worse than the 2008 financial crash.
He told Sky News's Sophy Ridge On Sunday he talks to Defence Secretary Gavin Williamson "quite regularly" about no-deal Brexit planning.
"I am committed to getting the best outcome for this country, which is supporting the prime minister's deal".
Saudi teen fleeing family granted asylum in Canada
A Saudi envoy in Bangkok denied any official Saudi involvement in Ms Qunun's detention, and her passport was later returned. Canadian Prime Minister Justin Trudeau says Canada will grant asylum to a Saudi woman fleeing alleged family abuse.
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