If there’s one piece of legislation that typifies the impact of Brexit, it’s the Government’s Immigration Bill. It abolishes free movement of people from Europe and delegates to ministers sweeping powers to set a new migration policy by Ministerial order, set out in a large ‘Henry VIII’ power. With the numbers in the Commons finely balanced, a few Conservatives deciding to rebel against the Government (as indeed did happen) could have had a massive impact – as long as the full ranks of Labour MPs also voted against. Yet this is where Labour’s leadership made a catastrophic error.

What we all expected was a strong three-line whip instruction to all Labour MPs to vote against this Immigration Bill on Monday morning was suddenly, without explanation, downgraded to a one-line whip ‘abstention’ instruction by Monday lunchtime. When challenged during the opening speeches, shadow home secretary Diane Abbott confirmed that Labour’s intention was indeed to abstain in the vote at 10pm, much to the shock and dismay of most Labour MPs.

Let’s not forget this Bill fails Labour’s tests on Brexit by sending a signal that Britain will introduce a restrictive immigration regime not compatible with full participation in the Single Market. Sacrificing free movement across Europe is a retrograde step and I suspect that a majority of Labour members would prefer it was cherished. The legislation also takes away the rights of EU citizens to work, study and live in the UK and therefore their rights to equal treatment and protections at work. Indeed, Diane Abbott wrote a full article on 26 January in the Morning Star under the headline “The latest Tory Immigration Bill will deepen the exploitation of workers”. So to have Labour’s frontbench suddenly step away from opposing the Bill and order an abstention was a staggering abdication of where Labour’s values should be at this crucial time.

It became clear during the course of the afternoon that a significant number of Labour MPs weren’t going to put up with this. And the numbers saying publicly they would rebel against the whip, determined to vote against the Government’s flagship proposal, grew larger. Even at the Monday night PLP meeting at first Labour MPs were told that abstention was our policy.

But then at 7pm a message was sent around saying “those colleagues who remain on the estate may wish to be aware that we will be voting against the second reading”. An eleventh hour u-turn, while certainly overdue, was hardly the clarion call to oppose this Tory legislation that Labour members and supporters would naturally expect.

The fact that the final vote took place in this relaxed ‘one-line whip’ mode may explain why too few Labour MPs were available to defeat the Conservatives. The Government coasted to victory by 297 votes to just 234 against, an unusually large majority of 63. Two Conservative MPs also decided to vote against the Government. But unfortunately only 178 out of 256 Labour MPs attended, presumably given the one-line whip status.

This was an utter shambles, with no clear explanation, rhyme or reason. Labour’s leadership must now explain this saga – and why they threw away this key chance to defeat the Government on such a bad piece of legislation.

Chris Leslie is Labour MP for Nottingham East