Will the real DUP Brexit policy please stand up? You can have whatever DUP Brexit you like at present.

There's the belligerent, backstop-free one, courtesy of Sammy Wilson, the party's Brexit spokesman.

If you prefer you can choose the time-limited backstop not ruled out by DUP leader Arlene Foster or MP Jim Shannon. Alternatively, there's a cuddly soft Brexit left open as a possibility by DUP Westminster leader Nigel Dodds (in, for example, a recent interview with ITV's Robert Peston) by which alignment to the EU customs union and single market would not necessarily be opposed, provided that Northern Ireland's Brexit-lite was identical to that of the rest of the UK.

There is, of course, common ground across the DUP that the backstop cannot remain in its current form.

That is part of the reason why Theresa May is still on mission impossible, seeking a codicil here, a new legally-binding paragraph there, all to no avail.

And if the DUP has offered some differences over how to change the backstop, they are mere amateurs at incoherence compared to our Prime Minister.

Having sold the backstop to largely receptive Northern Ireland communities beyond the unionist parties in December, Mrs May has spent recent weeks disavowing her own handiwork.

The Conservatives' European Research Group (ERG) Brexiteers are happy to use DUP opposition to the backstop as their battering ram to break the EU withdrawal agreement.

Yet it is mistaken to think that 'DUPERG' is a united cohesive entity. Many of the ERG are 'clean-breakers' from the EU, happy for the UK to leave without a deal. For all their apparent comradeship with the DUP, some of them could barely locate Northern Ireland, let alone the border, on a map.

Although it might not appear so from gung-ho Sammy Wilson's alpha male-ing on television, the DUP's position is less obsessed with a clean break from the EU and more concerned that none of the terms of that departure are Northern Ireland-specific. Listen closely to what the cerebral Dodds carefully says.

For the DUP, Brexit, hard or soft, has to be UK-wide. For many in the ERG, a hard Brexit is the goal, presumably en route to their "special place in Hell" allocated by the president of the European Council.

As it left behind nonsensical Paisleyite denunciations of the EU as a Catholic club, the DUP's Euroscepticism shifted from scripture to sovereignty. This led to a slight softening and the party flirted briefly with dropping its anti-EU stance prior to the Brexit referendum. It supported David Cameron's attempts to renegotiate our EU membership, making this clear in its 2015 Westminster election manifesto. The 2017 manifesto lamented the EU's "deafness to change in those negotiations" which meant that the DUP, unlike the UUP, preserved its opposition to the EU.

As is often the case, the DUP was in tune with its voter base, 70% of whom backed Leave, although at least one member of the DUP Assembly Executive team voted Remain. Yet the DUP did not expect a Leave vote and had undertaken zero preparations for such an eventuality. Belatedly, the party has begun to produce post-Brexit policy documents, but thus far the two offerings amount to critiques of EU regional and fishing policies, not a clear vision of how Northern Ireland will cope after March 29.

Many question the wisdom of the DUP's opposition to the backstop, given the potential economic damage to Northern Ireland of a no-deal Brexit. Business and farming leaders have made clear their view that a backstop makes good economic sense, and nationalists also see political value. The DUP's fear is that without the unilateral entitlement to end the backstop, Northern Ireland will be forever placed closer to the rest of Ireland and the EU - and it was always unlikely that any unionist party would acquiesce. The one-time Remain-supporting UUP also dislikes the backstop.

The withdrawal agreement does create potential barriers to trade between Great Britain and Northern Ireland in respect of goods heading to the EU single market. A joint UK-EU committee will review arrangements "with a view to avoiding, to the extent possible, controls at the ports and airports of Northern Ireland".Given that one of those airports (Belfast International) can barely deal with the people travelling through it at present, one shudders to think what will happen when checks on goods are implemented. These problems are for the future; GB-NI-EU regulatory divergence is a long way off, but they are live issues.

For now, though, the DUP should be clearer whether it is seeking to rewrite, time-limit or reject the backstop. It also needs to state its preference if none of those options are possible, which, amid all the noise, still seems to be the case.

Jon Tonge is Professor of Politics at University of Liverpool and co-author of books on the DUP and UUP

Belfast Telegraph