There can be no better illustration of the disconnect between the people and the Tory leadership than its wilful ignorance of the sheer scale of the growing countrywide opposition to its mindless stampede towards a no-deal Brexit. A poll by Hope Not Hate released on Monday will show that, by a margin of two to one, British people think that the economy, their families’ economic prospects, inward investment into the UK and even their exposure to terrorism will take a turn for the worse if we crash out of the European Union on 31 October. Only 17% of women think no deal would be good for Britain.

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They are right to be worried: the no-deal Brexit we are now being offered is not the Brexit promised before and during the referendum. “What most people in this country want is the single market, the common market”, Boris Johnson is on record as saying, along with “Personally, I would like to stay in the single market”. “Wouldn’t it be terrible if we were really like Norway and Switzerland? Really?” said Nigel Farage. “They’re rich. They’re happy. They’re self-governing.”

Yet if no deal goes ahead on Thursday 31 October, it will be nothing like Norway or Switzerland. By the following day – what Brexiteers will call “Freedom Friday”- there will be long queues at Dover and by Saturday 2 November many of our motorways will be at a standstill. By that Sunday, food prices will be going up – a 10% rise is the latest estimate – and by Monday the pound will be sharply down on its pre-Brexit value. By Tuesday medical drugs from mainland Europe will be less accessible, and a week after Brexit, companies will be complaining that vital stocks and components are not reaching them, bringing the threat of having to put workers on short time, and economists who have long forecasted recession will not be surprised.

All of the above is not a “project fear” fantasy, but the most conservative conclusions of an assessment by the UK’s most senior civil servant, which was leaked in April. These conclusions have been backed up by the independent Office for Budget Responsibility, the National Institute of Economic and Social Research, a Commons committee report and countless others.

Indeed, as revealed in a little-known table in a Treasury study last November, a no-deal Brexit could cost the country nearly £100bn in lost revenues and higher social security costs, far beyond the £26bn of “headroom money” that Tory leadership candidates have handed out over and over again to fund their various notions.

When future historians look back, they will be shocked to discover how such an act of economic self-harm that runs wholly counter to the national interest could ever be portrayed by Nigel Farage and Boris Johnson as the height of patriotism, and criticism from any quarter dismissed as a betrayal.

Play Video 1:02 Philip Hammond says he 'greatly fears' impact of no-deal Brexit – video

Even if some of the immediate chaos forecast by officials is averted on the day, the long-term economic impact of no deal is where the calamity lies. British history includes self-inflicted wounds – military disasters such as the Charge of the Light Brigade and the fiasco of Gallipoli – but no peacetime act of self-harm can rival exiting the EU without a deal when we are so woefully unprepared. Even now the new European commission president is offering to deliver us from this fate – and we are refusing the help. But for the Brexiteers there is little consideration of the consequences of what they propose. Their mission is driven by belief, emotion and ideology and the vehemence with which allegations of “betrayal” and “treachery” are thrown around reveals a profound crisis of identity.

For what message do we send about what kind of Britain we now are if we reject out of hand last week’s European offer to ditch the cliff-edge, and boast instead that we will not pay the money we owe to the EU: the equivalent of declaring an economic war on our neighbours? Brexiteers may be trying to reinvent a “Britain alone” Dunkirk spirit – once again showing its indomitable fortitude. But this all too easily descends into an inward-looking, intolerant and adversarial brand of paranoid nationalism bent on blaming all who disagree.

MPs can and should still prevent no deal. Parliament last week voted against its own prorogation, and Boris Johnson is now more likely to call a final Commons vote between his no deal and staying in the EU. Brexiteers who have campaigned for decades to restore parliamentary sovereignty will argue that a sovereign people cannot be undermined by a now non-sovereign parliament.

Having been an MP for half my life, I well understand the duty an MP has to listen to their constituents – the Brexit referendum reveals grievances that must be addressed – but also the obligation to weigh the balance of risks before a parliamentary vote as important as this.

For each member will have to explain a no-deal Brexit to the mother in their constituency whose child is suffering or even dying because lifesaving drugs cannot get through, and to the small businessman or woman seeing a lifetime’s work ruined and the livelihoods of their workforce with it. MPs will still receive their salaries, and from its new office in Dublin, inside the EU, the City firm co-founded by Jacob Rees-Mogg will still make its millions. But the other 649 MPs must recognise the plight of the less well-protected, whose prospects this mindless course of action so needlessly destroys.

• Gordon Brown was UK prime minister from 2007 to 2010