Britain is to due to leave the European Union at the end of March, but Khan warned the country now faces two "incredibly risky" options ― both of which could have devastating impacts on the economy and people's living standards.
Theresa May's comments on the issue this week mark the six-month countdown to Britain's formal exit from the European Union on 29 March, 2019.
Meanwhile, speaking on BBC One's The Andrew Marr Show, Michael Gove the Environment Secretary thinks her plan, agreed at Chequers in July is the right one for the moment.
The two sides hope to strike a deal on divorce terms and the outlines of future trade by November, so that individual member states can approve it before Britain leaves in March.
Keir Starmer, Labour's Brexit spokesman, said any EU deal must meet Labour's key Brexit tests, which include delivering the "exact same benefits" as Britain now has inside the single market and customs union.
"Let's be clear about this, under "no-deal" there would be some short-term disruption".
But failure to get a deal would lead to a contraction, she said.
International Monetary Fund chief Christine Lagarde said Monday that "all the likely Brexit scenarios will have costs for the United Kingdom economy", and a no-deal Brexit "would impose very large costs". Earlier this month, the Office for National Statistics said the economy had grown by 0.6% over the three months to July - the fastest pace in nearly a year.
Tottenham 1 Liverpool 2: Wijnaldum and Firmino sound Reds' title intentions
He added on Alisson's excessive fee: "I think the goalkeeper - like a centre-half or centre-forward - comes at a premium now". No, it was Romelu Lukaku - in the 89th minute - charging 60 yards to make a tackle in his own right-back position.
"I very much hope and pray that there will be a deal between the European Union and the United Kingdom", she told reporters.
Mr Johnson said the European Union's fallback position for the Irish border would mean Northern Ireland was "annexed" by Brussels. The Conservative government's handling of negotiations has been so poor, he said, that now he can't see any alternative to giving Britons another chance to stay in the EU.
"It would be a lot more wise to put her cabinet together, agree on what they want to agree on Brexit and how to get there, and then trigger this process", he added.
Known as the "People's Vote", the second vote idea is gaining traction among some politicians, unions and business leaders who argue that the public should effectively get a say on the final negotiated deal.
The boss of Britain's biggest carmaker Jaguar Land Rover (TAMO.NS) warned last week about the impact of Brexit on manufacturing and the company said on Monday it would go down to a three-day week temporarily at its Castle Bromwich plant in central England.
"The whole thing is a constitutional abomination", Johnson, who has previously compared the plan to a "suicide vest", wrote in The Daily Telegraph.
There is feeling around Westminster and Brussels that a Brexit deal could be within touching distance.
May also insisted no other plan on the table would ensure "frictionless" trade on the island of Ireland. Northern Ireland is part of the United Kingdom.