Not for the first time, the Labour Party is set to adopt yet another new position on Brexit. We don’t yet know exactly what Jeremy Corbyn will say in his forthcoming speech, but the heavy implication coming from Emily Thornberry and others is that he will support a new customs union with the EU.

In practice, of course, behind the spin we may well see another Corbyn fudge which seeks to close off criticisms rather than address reality. Just think of their old line about replicating “all the benefits” of the Single Market but without any lost power or free movement – that excuse lasted the Opposition for months, despite being completely fantastical.

This is the same gravity-defying illogic that claims nationalisation won’t cost a penny, and they don’t mind using it. So don’t be surprised if Labour’s new “aim” is a moon-on-a-stick Brexit of one sort or another.

The concept of some kind of replicated or partial customs union offers some convenient upsides to Corbyn. It wouldn’t necessarily require free movement, which could square away some of the Labour MPs worried about the more UKIP-ish Leave voters in their constituencies. And it might placate some of the more obsessive EU fans on his benches, who’ve talked themselves into believing that any sort of independent trade policy is impossible, despite the success of most of the world in doing just that.

I do wonder, though, if Labour have fully thought through the implications of a Turkey-style partial customs union.

The effective abandonment of the power for the UK to set its own trade policy and strike its own trade deals might not seem like a bad thing if you find trade suspiciously capitalist. It would mean ditching new economic opportunities, but Labour might not mind that given they don’t appear to even support economic growth any longer.

More dangerous to their position is the fact that a Turkey-style arrangement does not just mean sacrificing the power to make our own trade deals in lots of areas. It means allowing the EU to open up our markets as and when it wishes, through its own trade deals, with no consideration of UK interests, or consultation with the British Government, and no improved access for British exports.

Here’s a description of that ‘deeply unattractive’ idea, written by none other than Barry Gardiner, Labour’s Shadow Trade secretary:

‘…were, say, the EU to negotiate an agreement with the US that was in the union’s best interests but against our own, our markets would be obliged to accept American produce with no guarantee of reciprocal access for our own goods into the US.’

Emily Thornberry describes such a relationship as a “partnership”, but in reality it is anything but, as I laid out earlier this week.

There’s a political danger, too. Consider all the concern – much of it raised by Labour – about the prospect of TTIP, the EU’s proposed trade deal with the United States. Its critics feared that it would open up the NHS to American companies.

Indeed, Corbyn was so worried about this possibility that he pledged to oppose the whole deal to avoid this risk, and the Government sought specific exemptions.

And yet the customs union plan apparently set to be adopted by Corbyn and the Labour front bench would allow the EU to do deals opening up our markets in exactly this way, with no power for Parliament or anyone else in the UK to prevent them.

Could Labour really be about to support a proposal which would allow the EU to offer up the NHS as part of its trade deals, without the democratic right for the UK to refuse?