I posted the same question twice on the Labour Party Facebook forum. This is my response to the extensive debate.

Why is the Labour Party considering leaving the EU when during the referendum campaign we believed that Brexit was not in the national interest, and would especially hurt those who have suffered most from the last years of Tory rule? We campaigned for remain and reform. What has changed?

Thank you to the hundred plus people who have offered comments. I have read them all and thought about them. This is my conclusion. There are really only two answers, and one tactical argument.

The first argument is that it would be impossible to implement our Manifesto under EU rules. My answer to that is twofold: that good legal opinion does not agree (http://renewal.org.uk/blog/eu-law-is-no-barrier-to-labours-economic-programme  ); and because we are so closely linked, economically and geographically, to the EU, it will continue to influence what we can do, we just won’t have a vote in what will be “their” rules any more. We will no longer be one of the leading players in EU policy, and the “reform” bit of our agenda will be out of our control. Given the damaging economic impact of any Brexit scenario, this is quite as likely to obstruct our manifesto as existing EU regulations.

The second argument is that people knew what they voted for, and an absolute majority rules. This is more complex. There are a raft of arguments, but fundamentally, it is clear that the deal which the Government negotiates (if it manages to) will bear little resemblance to the promises made by the leave campaign (embodied in our six tests). Many of those promises were incompatible with each other, and some are impossible (like a solution to the Northern Irish border with the UK outside the EU). The only thing which will definitely happen is that we will lose our votes in Europe (our MEPs, our seat on the Council, our Commissioner, and our place in the innumerable working groups and projects which are shaping Europe).  So what people will get if we accept the Tory deal will not be what they can have voted for. This is as much a betrayal of the “will of the people” as reversing the Brexit decision without a vote.

Most of the people who voted were not stupid, or racists (or any of the other abuse which people have fabricated about them). Many had thought seriously about the issue, but since they are not going to be offered what they voted for they are entitled to say whether they want it, or whether it would be better to stay with what we have, to work for reform from inside the tent.

Finally, the tactical point. Since the general election the Tories have been desperate to blame Labour for their failings. Any appearance of backing a remain campaign before we could see the offer would have been a gift to them, so we were right to avoid this by appearing to prevaricate. However, less than 6 months from Brexit day, we should be clear that when Parliament rejects the government’s deal, and we seek a general election, our manifesto must be clearly in favour of putting the question back to the people. This is the best that Brexit can mean, are you sure that it is what you want?