The country that casts itself as leader of the free world has turned overnight into the global authoriser of racism, torture and climate-change denial. It was once the world’s beacon of democracy and the rule of law, but now Donald Trump’s executive orders challenge those constitutional fundamentals, giving comfort to dictators everywhere.

That unseemly dash to be first hand-clutcher is already an embarrassment from which a tight-lipped No 10 struggles to rescue a little dignity. After all, nothing has changed since her obsequious state visit invitation – Trump is only carrying out the ban he pledged. Any claims of a “special relationship” should die on the lips, after Boris Johnson’s feeble response yesterday.

This is the pivotal moment for Britain. Who are our true friends and allies, who share the most history, culture and mutual understanding? Trump’s arrival asks that question with a stark new urgency: the answer is not him, not his United States. Our safest haven is the European Union. This is no time to make ourselves the vulnerable vassals of Trump’s every whim, when we could stay as equals in a democratic partnership with our nearest neighbours.

Our safest haven is the EU. This is no time to make ourselves the vulnerable vassals of Trump’s every whim

Today the bill to trigger article 50 comes to the House of Commons. Here begins a national disaster, sadly worst for many Brexit voters. It is the first duty – the patriotic duty – of elected politicians to protect citizens from danger and promote their wellbeing, as they see it. Yet out of cowardice or political self-interest most will vote this week for what they think will profoundly and permanently damage their electors.

A quarter of MPs will joyfully vote us out of the EU, because these Europhobes sincerely believe this wayward self-destruction is in the national interest. But three times more MPs never supported Brexit, knowing it to be an error looking more damaging by the day. Still, they will vote for it all the same. Ignoring Edmund Burke’s instruction to act as representatives and leaders, instead they will cravenly follow what a small majority thought one day in June.

They “respect” the result of the referendum, they repeat nervously. Why? It was a consultative vote that failed to define Brexit on what terms, with what sacrifices or at what price. So foolishly certain were both main parties that they would swing a remain result, they agreed a referendum without setting a threshold beyond a bare majority. They added no mechanism for agreeing an unknowable Brexit deal at the end of negotiations. MPs should now salvage and repair some of that negligence.

Amendments put forward by Labour and others would offer some protection from the prime minister’s rock-hard Brexit. Labour’s amendments call for resident EU nationals to stay: embracing them warmly would be the right rebuke to Trump. Parliament should get regular updates and a vote on the final deal before it’s set in concrete by the European parliament. How ominous if May throws out amendments protecting workers’ rights and anti-tax evasion laws. One essential amendment requires unimpeded tariff-free access to the single market. All these must be red lines for pro-European MPs of all parties, before they press the trigger.

But Jeremy Corbyn has three-line whipped his MPs to vote for article 50, willy nilly, rendering these amendments pointless. The staggering ineptitude of Labour’s approach has fragmented the party along new lines, with remain- v Brexit-voting seats. What a dismal spectacle to see life-long pro-Europeans in Brexit-voting constituencies crumpling to “respect the will of the people” for fear of losing their seats. Those who rebel are virtually all in remain seats, where that “respect” is simpler.

Labour MPs caught in that dilemma plead their working-class voters’ indignation at immigration, suppressed wages, over-run public services – even though many of these seats have few migrants: relatively few are like the much-quoted Boston or Barking. These MPs defend themselves by sneering at “metropolitans” who, they say, don’t understand north-eastern or Midland seats.

I would reply to them that they have a deeper duty to their voters than obeying how they voted that day. MPs’ duty is to lead and defend their people from Brexit’s reduced living standards. Make the case. Stand by what you believe and explain why Brexit will harm them, their children and their grandchildren. Talk about why a stable alliance in which we have an equal voice is stronger than the haphazard chance of trade deals with the likes of US, China or the Gulf – none the size of our EU trade.

Nor is this primarily a class question: the old are more to blame for Brexit. But as older cohorts drop off the perch, Labour MPs should stand up for the new young voters reaching the register. They say economics can’t win the EU argument alone – though if brutal Brexit predictions turn horribly real, that will change. If emotional patriotism matters most, then our sovereignty is safer with Europe, not demeaning our sovereign in a golden carriage ride down the Mall with Trump. Our status in the world is stronger as a leading EU member than alone, striking dishonourable deals with dictators. Shunning Trump and re-embracing Europe best reflects British values, who we are, what we believe and what binds us to democracies like ours: it’s not too late.

Looked at cynically, Labour has nothing to lose by standing up for what virtually all Labour MPs believe on the EU, as do two-thirds of Labour voters. Electorally Labour is in freefall, 14 points behind in the polls, not even best trusted on the NHS: shocking that there’s any possibility of losing byelections in Stoke-on-Trent and Copeland.

On this great issue of our generation, Labour has been incoherently, embarrassingly irrelevant. If we pro-Europeans are wrong, if Brexit is a triumphant success, trade blossoms, growth booms and Britain stands tall alone, Labour is done for anyway. May will be prime minister for as long as she wants, Tories in power beyond the blue horizon.

Labour MPs in Brexit seats may lose their seats anyway, unless the party comes to its senses soon. They would earn more respect from constituents by taking a principled stand, explaining why they are determined to protect them from a bad Brexit. What have they to lose? Voters will spot the dishonest prevarication if MPs put clinging to their seats first. Labour has drafted wise safeguarding amendments. Labour MPs must fight for them. Certainly they must reject the absurdity of being whipped by life-long rebel Corbyn.