On Friday, I sent out a tweet, purely on impulse. It said that we, the Labour Party, must be the party of Remain. The response was, quite unexpectedly, tremendous, with hundreds of likes and retweets. The argument clearly has resonance.

We are living in perilous times. It is no exaggeration to say that the Labour Party is facing an existential threat. Our ability to deal with the issue of Brexit may well determine whether or not the party has a future.

And so far we have been found wanting. That is not a criticism of Keir Starmer, who is making heroic efforts to work out a coherent policy. The problem is that we are perceived as sitting on the fence, by stating publicly that we accept the referendum result while trying to put legalistic barriers in the way of Brexit.

We must go back to first principles and be entirely honest before we get into the practicalities of what we should do in the light of the referendum result. The attempt to straddle both camps has clearly failed, as the recent by-elections in Richmond Park and Sleaford and North Hykeham, as well as current showing in the polls, demonstrate all too clearly. We have prevaricated and triangulated to such an extent that we have been squeezed on both sides, by leavers on the one side supporting the Tories, and Remainers on the other opting for the Lib Dems. It is the path to oblivion.

The first test of whether we support Brexit is simple. Do we think that it would be a good outcome either for Britain or its people? More specifically, do we think there are any advantages to leaving the EU? Those in the party who suggest we must obey the result of the referendum fail to address this fundamental point. My view, and that of probably most of the population now, is that Brexit is bad for Britain. It is bad, too, for the British people. It is defeatist and mistaken to suggest “we must abide by the result” even if we know it will be a disaster.

Instead of worrying about the potential electoral implications of fighting to stay in the EU despite the referendum result, we should be highlighting the disaster that Brexit will be. If we know that leaving is damaging for our economy and our people, then we have to say so. Loudly and clearly. And with a united voice.

This seems self-evident and yet no one seems to be articulating it. Nearly all our MPs supported Remain. And two thirds of our supporters did so. It is not, therefore, just a few of the “liberal elite” who want us to stay in. It is the millions whose jobs are threatened, whose wages will be reduced and whose ability to travel cheaply abroad may be curtailed.

Of course I was campaigning in a strong Remain constituency in the Richmond Park by-election. But putting up a Brexit candidate in Sleaford hardly delivered any extra votes either. If remaining is the majority view in the party, then surely we should adopt that policy positively and emphasise it in our speeches.

We all accept that the referendum process was fundamentally flawed, both in terms of the question that was asked and the way the campaign was conducted. We should not therefore be paralysed by its result. Constitutionally, the referendum is not binding and just because the Remainers lost does not mean we should not continue the fight. Let’s say there had been a referendum to abolish the NHS and the answer was yes: would we simply acquiesce and say the people have spoken? I think not.

Politics is extremely fluid at the moment. Look what has happened in Scotland or to the French Parti Socialiste. As more and more bad news emerges, Brexit itself could become unpopular as quickly as it gained momentum. The Labour Party has to be ready to take advantage of that situation.

We are the Opposition. We should oppose what the government is doing when it is damaging Britain. We will undoubtedly lose some people along the way. A minority in the party will not like it. But we will gain others. Of course it is a gamble. But less of one than sitting on our hands while the party haemorrhages votes because we lack the courage of our convictions.

Christian Wolmar was Labour’s candidate in the Richmond Park by-election and is a leading transport author.