The UK parliament's Committee on Exiting the European Union has warned that a 'no-deal' Brexit would lead to severe disruption, pose a fundamental risk to the competitiveness of key sectors of the British economy and put many jobs and livelihoods at risk.
The report comes in a week when the UK government and the contenders to be the next British prime minister have been talking up the prospects of a no-deal Brexit at the end of October.
The committee spoke to key industrial sectors including car makers, farming, pharmaceuticals, and data dependent companies before compiling its report.
It said all those sectors would be hit hard, and geographically a 'no-deal' Brexit would inflict the most damage on the northeast and the west midlands, with "the chemical, retail, food and drink and manufacturing sectors … hardest hit".
The report also found that without a deal the UK could not rely on Article 24 of GATT [General Agreement on Tariffs and Trade] to maintain the current tariff free trade regime with the EU.
Committee Chairman Hillary Benn said: "A no-deal Brexit, with no GATT XXIV 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."
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The committee heard evidence from the pharmaceutical industry that a no-deal Brexit would be a "leap into the unknown", potentially putting patient safety at risk and increasing costs for the health service.
The MPs also 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.
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".
The report was opposed by four Tory Brexiteer members of the committee - Jacob Rees-Mogg, Peter Bone, Andrea Jenkyns and Christopher Chope.
Elsewhere, the Minister for Foreign Affairs will be in Brussels this afternoon to meet the EU's Chief Brexit negotiator Michel Barnier.
They will discuss Ireland's no-deal contingency plans and recent meetings between the taskforce and British negotiators.
A spokesperson for Tánaiste Simon Coveney said he would also thank Mr Barnier and the taskforce for their continuing determination to safeguard peace on the island of Ireland and to protect the EU single market while respecting the UK's decision to leave the EU.
Additional reporting Michéal Lehane and PA