A no-deal Brexit could cause "severe disruption" to the economy and put jobs and livelihoods at risk, MPs have warned in a damning report.
The Commons Exiting the European Union Committee heard evidence from the pharmaceutical industry that a no-deal Brexit would be a "leap into the unknown".
Patient safety could be put at risk and costs for the NHS may increase, the committee was told.
The MPs said there was no reason to doubt concerns that there could be "interruptions to food supplies in respect of certain products" because of the "disastrous" impact on UK farming.
And they warned that tariffs adding £2,700 to the cost of British-made cars in European Union markets would but the sector at a "competitive disadvantage".
Seventeen Conservatives defied a three-line whip - including a senior minister, Margot James, who later resigned.
About 30 ministers did not vote, including Justice Secretary David Gauke, who earlier said suspending parliament would be “outrageous”.
The report - which was opposed by four Tory Brexiteer members of the committee - cast doubt on Tory leadership hopeful Boris Johnson's claim that the UK and EU would be able to maintain existing rules while they negotiate a free-trade deal.
Mr Johnson has argued that a provision under the General Agreement on Tariffs and Trade - known as Gatt 24 - could be used to avoid tariffs under World Trade Organisation (WTO) rules for up to 10 years.
But the committee said: "It requires an agreement between the two parties, a plan as to how the end state will be reached, and for this agreement to notified to all parties to the WTO.
"By definition leaving without a deal means there is no agreement."
It said that Gatt 24 therefore "does not provide a means to mitigate the risks to EU-UK trade in the event of a no-deal exit".
The MPs who opposed the report were European Research Group chairman Jacob Rees-Mogg, a prominent supporter of Mr Johnson, Peter Bone, Andrea Jenkyns and Sir Christopher Chope.
Mr Johnson has built his Tory leadership campaign around a "do or die" commitment to leave the EU on October 31, with or without a deal.
The committee's chairman, Labour MP Hilary Benn, said: "A no-deal Brexit, with no Gatt 24 agreement, would be at best a foolhardy gamble and at worst, lead to severe disruption, and it is neither desirable nor sustainable as an end state for our economic relations with the EU.
"This clear evidence reinforces our previous conclusion that a 'managed no deal' cannot constitute the policy of any responsible government."
A Department for Exiting the EU spokesman said: "As the Secretary of State set out to the Committee this week, we've been preparing for nearly three years to minimise disruption in the event of no deal, and we have over 300 work streams looking at specific no-deal plans across a range of sectors which are well advanced, with departments making sensible decisions about prioritisation.
"We continue to provide people and businesses with the information they need to prepare, and encourage them to take action to avoid disruption."