Every MP who voted for the Brady amendment last night to reject the Irish ‘backstop’ was playing games with the Irish peace process and should be ashamed of themselves. Their votes showed they either don’t understand the complexities of Northern Ireland or, if they do, they just don’t care about the potential for economic and social catastrophe their vote could unleash. The message – that Good Friday Agreement, open borders, mutual respect for identity are all up for slaughter on the altar of Brexit – could not have been clearer.

Labour MPs who backed the Brady amendment, or abstained without good reason, should feel particularly ashamed. Bringing peace to Northern Ireland was a signature achievement of the last Labour government – something of which I am personally very proud, having played a role in it – and to sell that so cheaply to a Prime Minister more concerned with holding her own party together than standing up for the national interest is appalling.

I can think of nothing at all that justifies a Labour representative siding with the right-wing extremists of Jacob Rees-Mogg’s European Research Group on this matter. What they were doing is backing Brexit come what Theresa May, regardless of the potential impact on the Good Friday peace process. The Brady amendment strips out the only really positive part of the Tory deal – the backstop guaranteeing an open Irish border.

This is not and never has been a game. The 3,000 people who perished in the conflict that raged from 1969 to 1998 all had friends and family who will carry the scars and hurt for the rest of their lives too. It might have been more understandable if the advocates of tearing up the backstop had some workable alternative to offer. But they do not, and they never have had a plan of their own. They are rejecting the backstop in the full knowledge that the only alternative is a hard border.

Make no mistake. A hard border in Ireland will be of benefit to smugglers and other criminals only. Doubtless portrayed by the New IRA and others as ‘the second partition of Ireland’, it will be grist to the mill by that tiny minority of republicans who rejected the Good Friday Agreement and who recently planted the car bomb in Derry/Londonderry to destabilise it. They have attempted to do the same over the last two decades in their aim of restarting a war that will not be confined to Irish shores.

The UK and Irish governments, along with the EU, were right to prioritise the Irish border in the Brexit negotiations. And although I strongly reject the Prime Minister’s deal, I cannot and will not join those attacking the backstop. Any Brexit deal of any kind must include this insurance policy. This rainy-day back-up plan, to be used in the event that a new UK-EU trade deal isn’t ready by the end of 2020 or beyond, is a sensible policy. It will only be employed if needed (and everyone hopes it won’t be) to ensure the border between Northern Ireland and Ireland remains open and invisible.

It’s not just that Ireland or the EU won’t accept it any other way: we in the UK shouldn’t either. We must protect what we’ve achieved in Northern Ireland together in the last 20-30 years – and avoid any hardening of the border. I call on everyone to stop playing politics with Northern Ireland and insist on an insurance policy over the border. We should also demand an end to attacks on the Irish government, which is merely fulfilling its obligations under the Good Friday Agreement in insisting on the backstop. Just as the UK should be doing.

It is simply no good politicians or commentators saying: “Nobody wants a hard border so there won’t be one.” There will be one if we don’t stop it. If we Brexit without a deal, both Ireland and the EU will have responsibilities in terms of ensuring protection of the single market and customs union and the UK will have its own responsibilities, including meeting WTO requirements. The blunt truth is that maintaining an open border always was the Achilles’ heel of a hard Brexit. It is not too late, though, to make up for these mistakes.

Yesterday’s votes changed nothing in that the advocates of Brexit are still chasing unicorns. In two weeks, the Prime Minister will return to parliament and will probably report that she’s been unable to remove the backstop from the treaty she previously agreed and signed with the EU. She may or may not get some warm words of comfort, but Labour MPs of all people will need to find the courage to defy the Prime Minister, reject a no deal Brexit and instead stand with the people of Northern Ireland – the majority of whom rejected Brexit in 2016 and still do today – in support of a People’s Vote.

Peter Hain is a Labour peer and former Secretary of State for Northern Ireland.