Henry Newman is Director of Open Europe.

A week after the biggest ever Parliamentary defeat, we are no closer to finding a way through on Brexit. Theresa May and her ministers have been meeting MPs from different factions. Yet the people I’ve spoken to in the room for those cross-party discussions say that few of those visiting 70 Whitehall showed interest in exploring compromises other than their own preferred solution. Some of those leaving the talks complained that they heard no new ideas from the Prime Minister, but that’s little surprise. We have been arguing about Brexit pretty much non-stop for three years.

There’s something odd about the current debate. Putting aside those at the extremes advocating No Deal or a second referendum, there seems to be a majority in the Commons in favour of a form of negotiated exit. However, there isn’t yet a majority for the Prime Minister’s deal. Most MPs in favour of a negotiated deal accept the need for some form of backstop (now a sine qua non for a deal), and also accept that major changes to the Withdrawal Agreement are unlikely. To put it another way: these MPs are (essentially) only arguing about the non-binding bits of the deal.

One category of MPs demanding a ‘Plan B’ are those advocating Norway Plus. But the truth is that Norway Plus is Plan A with a bow on top. It’s a plan which even its proponents admit is premised on accepting every binding part of Plan A. All that would change is a narrowing of the destination outlined in the Political Declaration to Norway Plus.

The Norway Plus plan has got through various evolutions, but the basic idea is to seek a long-term relationship with the EU which keeps the UK inside the Single Market (the Norway part) and the Customs Union (the plus bit). That would, proponents suggest, obviate the need for the backstop. Putting aside the fact that during the referendum leading campaigners, from Michael Gove and Boris Johnson to David Cameron and George Osborne, unequivocally ruled out the UK remaining in the Single Market, there are many issues with this plan.

First, it’s often suggested that Norway is an off-the-shelf model, ready to adopt. Actually, things aren’t so straightforward. There are two broad paths to Norway Plus. Both require negotiation. Either the UK would accede to the European Free Trade Area, while getting a derogation from EFTA’s free trade deals (which would be incompatible with an EU Customs Union), as well as agreeing a move to the EFTA ‘pillar’ of the EEA agreement. Or the alternative is to negotiate a new pillar of the EEA Agreement – a major change to a treaty with 30 state parties.

Second, negotiating a path to a version of Norway Plus would put the UK under huge pressure to agree further strictures, which would likely leave us with a far worse deal. Many in Brussels and member states are worried we are too big to be treated like Norway. They want tighter rules on services (especially financial services). Some want to keep us in the Fisheries Policy and the Common Agricultural Policy. Others want tighter enforcement rules. We will probably be asked to pay more money than Norway does. What leverage would the UK have to resist these extra demands if we had signed the Withdrawal Agreement and committed to getting to ‘Norway Plus’? We would be over a negotiating barrel, trying to agree the required protocols or derogations as the clock ticked down and pluses kept being added. MPs can call for a ‘Common Market 2.0’ but that’s just a slogan – not something anyone has agreed with the EU or EEA.

Would Norway Plus be sustainable in the long-term? Probably not. A senior Elysee source told me he thought it was inevitable that the UK would either break such an agreement by pushing back on obligations, or cancel the deal by demanding a new arrangement. Why? Because Norway Plus would leave us extremely close to the EU, far closer than Theresa May’s deal. It could – depending on the number of pluses – leave us as essentially as a non-voting member of the EU, subject to wide ranging rule-taking.

An alternative path to a negotiated deal is put forward by the Labour Party. Last night ,Labour proposed an amendment demanding a vote on a permanent customs union with the EU and a “strong relationship with the single market”. There already is a customs union in Theresa May’s deal – it’s at the heart of the backstop and could only be replaced if both the EU and UK agree. So it’s unclear how exactly this differs from anything Labour could negotiate, although Labour claim their customs union would come with control over trade policy, something the EU won’t offer now. It’s also unclear how their relationship with the Single Market would work, but they accept it would be “underpinned by shared institutions and obligations” and would entail wide spectrum rule-taking, or “dynamic alignment on rights and standards.” So far, of course, the EU have said you’re either in the Single Market or you’re not. Partial dynamic alignment was proposed by the UK at Chequers and has again so far been rejected by the EU.

Over the next few days, Parliament will seek to wrest control of Brexit. But although some claim that the facts around leaving the EU have become clearer since the referendum, a quick glance at Hansard for the last couple of weeks reveals a serious amount of magical thinking and unicorn-chasing from MPs on all sides. A series of indicative votes won’t necessarily bring greater clarity but would risk a majority coalescing around a policy which is simply un-negotiable.

Ultimately, there are still only three basic choices: No Deal, No Brexit, or a version of the Prime Minister’s deal. Yet MPs have passionately dug in, as they cling to their ideal options. The deal on the table is far from flawless, and needs some improvement. But it represents the safest path to delivering Brexit and already leaves a spectrum of future possibilities open – from a close Norway Plus relationship to a far looser arrangement.

Following last night’s Labour amendment there will also soon be a vote on a second referendum. As the risk of losing Brexit entirely grows, will more Eurosceptic MPs come around to Nadine Dorries’s view that the deal just needs to be got over the line? Or to the argument that Jacob Rees-Mogg repeated over the weekend that the deal, though flawed, is better than Remain? Until they do, there’s little possibility of securing Brexit, and a high chance that any exit is on far softer terms than most Conservatives would desire.