The latest government defeat on Brexit should be a watershed. Thursday’s 45-vote defeat, in which scores of MPs abstained, says something lethal about the parliamentary Brexit process. Opposition amendments from Labour and the SNP were duly defeated, as expected. An important all-party backbench amendment was withdrawn at the last moment, leaving key issues again unresolved. And the government lost another vote because of Conservative splits, exposing the bankruptcy of Theresa May’s Conservative-facing Brexit strategy and reinforcing the need now for an all-party consensus approach. All of this underscores that, even at this late hour, Brexit must be decisively changed by determined MPs of all parties and by effective leadership if the national interest in the Brexit endgame is to be defended and preserved to some degree in this grim process.

It was a humbling day for the prime minister and the Tory party. At a time when supermarkets, health authorities, police chiefs, manufacturers and service industries are all raising their Brexit threat levels to critical; in the week in which government plans to run extra ferries between Kent and the continent fell apart so abjectly; and 48 hours after MPs were told it might be 10 years before the “alternative arrangements” on which the entire recent Tory truce on the Irish border rests might be viable, it might have been supposed there would have been more of a sense of national peril in Thursday’s exchanges.

That proved to be naive. Instead, Mrs May did not even attend, other than to vote. She was, it was said, making calls to European leaders, though there is precious little evidence that they are in negotiating mode; and they are even less likely to be after this latest defeat. Meanwhile, the main speculation at Westminster centred on whether the Tory fanatics (who were also conspicuous mainly by their absence from the chamber) would deign to back the PM. As the Labour MP Yvette Cooper, who continues to be a rare beacon of non-partisan clarity in this process, rightly complained, parliament is increasingly at risk of “just drifting” into creating avoidable negative outcomes that will affect lives in all parts of the country for years to come.

A large part of what is so reckless about this process is that the row between the fanatics and the government centres on rightwing dogmas not facts. At issue this week were the words in the prime minister’s bland motion, part of which reiterated “its support for the approach to leaving the EU expressed by this house on 29 January”. That “approach” to Brexit included the vacuous Graham Brady amendment, which required the government to replace the backstop by alternative arrangements. But the house’s approach on 29 January also included the Caroline Spelman amendment, which rejected leaving the EU with no deal. Both were passed but, to the fanatics, only Brady was acceptable. This explained why, at the very start of Thursday’s debate, the Brexit secretary, Stephen Barclay, had to confirm to David Davis that the UK would be leaving the EU on 29 March if there is – as some fanatics hope – no deal. That brief exchange encapsulated the haplessness of recent Commons Brexit proceedings, because it was both misguided and unavailing. The assurances made no difference. This is hopeless stuff for matters of such importance. It reeks of failure.

In two weeks’ time, parliament will face the same serious issues again. The options have confronted it ever since the leave vote in 2016 and since November’s deal in Brussels. Parliament can no longer allow itself to be complicit in Mrs May’s strategy of running down the clock and selective accountability. As several MPs – notably Kenneth Clarke, another beacon – pointed out, it may now be too late for the Brexit process to be salvaged by the passing of mere motions, even when they cross party lines. This is why the time has come for parliament to get behind Ms Cooper’s all-party plan to use legislation to take back control of the Brexit process – and extend article 50 – from Mrs May’s Tory-focused approach. The prime minster’s approach has failed. It is taking Britain towards a no-deal outcome based on idiotic and destructive dogmas. The time has come to forge a new consensus to save the country.