Labour’s decision to whip against the EU withdrawal bill might well have more of an impact in the Lords than the Commons. In the Commons, as I wrote on Monday, the number of Tory rebels might well be offset by Labour ones—and I suspect that Labour’s decision to whip against the bill at second reading will make it easier for the Tories to peel off Labour rebels on amendments later on. But in the House of Lords, the government doesn’t have any sort of majority. If Labour whip against it there and team up with Liberal Democrat and cross-bench peers, the bill could end up only passing with significant amendments.
Now, normally the House of Lords backs down when it is in dispute with the elected House—as it did on Article 50. But it is far from certain that it would on this bill. First, the election result has emboldened Remainer peers and secondly a sufficient number of Lords feel strongly enough about the implications of this bill to defy the Commons over it even if this risked prompting a constitutional crisis.
If the Lords does pass amendments and then won’t back down, the government will have a serious problem. For there would not be sufficient time to parliament act the bill before March 2019. Secondly, it is far from certain that the parliament act could be used on this bill given its constitutional implications.