In a strange new twist, Theresa May has replied to Labour’s suggestions on Brexit in terms so opaque that this newspaper has interpreted them as a rejection of Jeremy Corbyn’s terms, while the Times believes her to be ready to compromise. Like the death throes of a chess game, the moves available to her are small and few, and it’s hard to figure out what decision she has taken.

In shadow Brexit secretary Keir Starmer’s lawyerly fashion, Labour’s terms were laid out fivefold: a permanent customs union; “close alignment” with the single market; dynamic alignment on workers’ rights, that is, for the UK to keep pace with the evolution of rights and protections in Europe; continued membership of EU-wide agencies and funding programmes; and an agreement on security arrangements such that we retain access to shared databases and the European arrest warrant.

Corbyn lays out Labour’s terms for backing May on Brexit Read more

The two major omissions were the Irish border, a problem that evaporates if we’re part of the customs union; and freedom of movement, which is becoming toxic for Labour. The party’s strategically ambiguous position – we accept that somebody has to do something about it at some point – collided with its values during the immigration bill. The decision to abstain on what was essentially hard-right legislation – vital workers classified as unskilled by dint of low wages – didn’t even last the length of the debate. In the grand scheme of Brexit unanswerables, it probably seems legitimate for the opposition to bury this conundrum in the interests of pragmatism, yet this episode has been devastating to many members, already dispirited by the party’s abject failure to speak up for the 3 million EU citizens disenfranchised by the referendum and disregarded since.

Anyway, if Starmer’s original six tests were, like Trotsky’s transformations, deliberately unmeetable, these five asks were different: the final two are unarguable. For all the absurd motives imputed to the leave vote, not even Boris Johnson at his flakiest and most ridiculous would claim anyone voted to shut off our access to international policing resources and shared research capabilities.

Alignment on workers’ rights would have been relatively easy for May to compromise on, since a future parliament couldn’t be bound by it; yet she has already rejected it, in favour of giving parliament the option of following Europe on a case-by-case basis. The Tories’ record on workers’ rights – doubling the time before you qualify to pursue unfair dismissal to two years, introducing tribunal fees that have capsized the number of claims brought, the Trade Union Act, which should be prefixed “Anti” – gives a very clear indication of how much cross-party cooperation we could expect on these case-by-cases.

“Close alignment” on the single market is more or less the direction May was going in anyway, for goods if not for services. Yet she cannot accept a customs union without splitting her party; and without it, the Irish border problem comes back with a vengeance, leaving everyone in the same situation they were in before, just with less time. Labour and the Conservatives are no longer in a battle against one another, if they ever were; both have 29 March as their real opponent, which is more dangerous for Corbyn than it is for May, given she has control of the timetable, at least at the time of writing.

Facebook Twitter Pinterest Theresa May speaks at the European Council headquarters in Brussels, Belgium, last week. Photograph: François Lenoir/Reuters

Starmer’s five demands were deftly and meticulously planned, to the degree that they look incongruous on the current terrain of burnt-out stumps of ideas and barren rhetoric. The letter was worded on the basis of what Labour already knew Brussels would accept; were May to fall in behind them, the path to withdrawal would probably be uninterrupted.

Yet even discounting the prime minister’s fabled stubbornness, it’s very hard to see what her incentive would be. The parties might, between them, get the deal over the line, but her leadership wouldn’t survive even if her party did. May can’t compromise on this, which puts them back to square one, at her almost universally unpopular deal, garlanded with bad-faith renegotiations that she already knows the EU won’t buy.

What Corbyn's terms for backing May on Brexit really mean Read more

Labour could have avoided this frustrating and tedious regression if it had ended its demands with, “if all this fails, a people’s vote”. It is, after all, what they agreed at conference: they would not enable a Tory Brexit; they would fight for a general election; if they couldn’t get one, all options would be on the table, including a people’s vote. Those hedging words “all options, including …” cannot stave off for ever, or indeed, for one more day, the obvious point that there are no other options. Tactically, it is the only Labour move that could meet May’s ultimatum – no-deal chaos – with an ultimatum of their own. Labour MP Matthew Pennycock spelt this out.

Starmer reportedly included the call for a second referendum in his original draft, then, by the time it had reached the prime minister, that paragraph had mysteriously dropped off. Why the Labour leadership continues to avoid the move is anyone’s guess, but it’s time to stop guessing: whatever the psychodynamic texture of Corbyn’s attitude to Europe, his primary and longest commitment has been to party democracy. Labour members and voters overwhelmingly want a second vote; the impact on Corbyn’s electoral prospects, if he fails to oppose Brexit, would be brutal – a report by the transport union, TSSA, estimates it would cost Labour 45 seats. But perhaps the more important question is, what would be left of his raison d’etre?

While this wrestling continues, the only concrete route to another vote is via a cross-party amendment put forward by Labour’s Peter Kyle, in which MPs would vote May’s deal through on the condition of a people’s vote afterwards. Four months ago, such an idea would have looked fanciful without the explicit backing of one of the major parties. Yet, with one party forsaking the national interest by using catastrophe as a bargaining chip, and the other ignoring its membership, the concepts of loyalty and discipline have become entirely subjective.

• Zoe Williams is a Guardian columnist