In every political generation there are decisions that history later reveals to be defining of an era. They are watersheds for individuals and governments, for the fortunes of political parties and entire parliaments. And the choices you make as a politician at these critical junctures are those that you have to live with throughout the rest of a political career, however long or short its course.

The vote on article 50 that will likely follow today’s supreme court ruling is the fork in the road for this generation of Westminster politicians. The decision we take, individually and collectively, will shape the future for our country and for our children, and it may also determine the fate of the current crop of MPs and the parties we represent.

I have reached the decision that whatever the impact on my career, however difficult it may be to swim against the Brexit tide, I cannot, in all conscience, stand by and wave through a course of action that I believe will make our people poorer and our politics meaner. I cannot vote to trigger article 50 on the wing and a prayer that Brexit will do as the prime minister says, and make Britain a fairer, more prosperous and equal society. Because I do not believe that is true.

Of course, I can’t know how Brexit is likely to play out, any more than Theresa May can. But my judgment tells me that the stirring and nostalgic vision she painted last week of a buccaneering Britain striking advantageous trade deals across the globe, while our longstanding competitiveness and productivity deficits are transformed at home, is a triumph of hope over experience, and party politics over the national interest.

Far more likely, in my view, is a protracted and painful withdrawal from the single market and customs union, alongside complex and contested negotiations to forge new free trade agreements and tariff schedules with not just the European Union, but also with all the states across the world with whom our current deals are derived via the EU. Perhaps all the bureaucracy, self-interest, high politics and low skulduggery that have characterised trade relations since time immemorial won’t apply to the UK this time, but I have my doubts.

And if those doubts are even half right, the impact on key sectors in the UK – manufacturing, agriculture, services and the City – will be to constrain activity and profits, jobs and investment. That, in turn, will reduce tax receipts, increase the deficit and trigger further cuts in public expenditure, hitting hardest working class people in places like where I live, who I represent.

Deciding to make a stand against triggering article 50, however, is about far more than the financial impact of Brexit. In truth, one of the gravest mistakes we made on the remain side, especially on the left, was to place too great an emphasis on the economic implications of the vote and too little on the political context and consequences of our withdrawal from the EU.

Too little effort was made to remind people of the role formal economic and social collaboration across Europe played in securing 70 years of peace on our continent. And too little thought was given to the catalytic effect Brexit might have on the forces of far-right nationalism that are resurgent once again in Europe, setting nation against nation.

Brexit Britain, like Trump’s America, is being held up by those far-right leaders as a beacon to light their countries’ way to the nativist (white), protectionist and illiberal future they have long aspired to. Differences in language and accent can’t obscure the common currents of xenophobia, bigotry and aggression that are evident across the west.

Faced with these dark trends, so reminiscent of our European past, the Labour party also has a collective choice to make. We can hedge and triangulate, appease and acquiesce, and hope to ameliorate the worst, in economic and political terms. Or we can take a stand for our values, for what we believe to be in the best interests of our people, our country and the wider world. It is a stand against the political lies that preceded the Brexit vote and the fantasy island economics that have followed it. A properly patriotic stand, which acknowledges the modern challenges of globalisation and migration, but warns against the age-old dangers of blaming the foreigner for all ills, and so rejects the shouty jingoism and deceitful promises of the Brexiteers.

I believe that leadership from Labour has to begin in parliament in the coming weeks, when we see the legislation to trigger article 50. We all heard the threat from May that she would pursue “an alternative economic model” if Brexit turned bad, and we all know what that means: a low-tax, low-wage, low-security economy, as dreamed of by generations of hard-right politicians. If that is even a remote possibility, then Labour has a duty to try and prevent it, in the interests of the people we represent. And the most democratic means to achieve that is to trust the people once more – all of them, including the 16- and 17-year-olds denied a say on their future – in a second, confirmatory referendum, once the reality of Brexit is revealed.

If May refuses to accept amendments that would insert such a failsafe device then it will be obvious to all that she is recklessly pursuing a Brexit of any sort, and at any cost, for party political reasons and at the expense of the British people. In those circumstances, I do not feel I would have any choice but to vote against the government and, if needs be, the Labour whip.

No doubt taking that stand will make me an enemy of the people in the eyes of the Daily Mail, or the “remoaner-in-chief”, as a rightwing radio host described me last week. But I was elected to parliament to exercise my judgment on behalf of the people I represent, and I can be ejected from parliament by those same people at the next election if they choose. That’s democracy – and I cherish it.

So whenever the election comes I will tell my constituents, with a clear conscience, that I stood up for my convictions, and what I believe to be their best interests. I will tell them that in parliament I tried to secure an opportunity for them to be certain that the Brexit description they bought on 23 June matched the goods that will turn up two years from now. I will tell them that I understand the economic and political frustrations they feel, but that leaving the EU will do little to relieve those frustrations, indeed it may compound them. And then I’ll take my chances with the people.