Since his surprisingly strong result in the general election, there has been renewed chatter amongst Jeremy Corbyn’s supporters about how they can crack down on his internal opponents.

This morning these efforts took concrete shape: the Daily Mail reveals that Momentum, the left-wing group which grew out of Corbyn’s leadership campaigns, has taken control of the constituency party of Luciana Berger, one of his high-profile critics.

Not only was she one of the (great majority of) Labour MPs who voted for the no confidence motion tabled against him, but Berger has been a victim of the anti-Semitism which has blossomed in the Labour Party under the current leadership.

Shortly after taking nine of the ten positions on the ten positions on the executive of the Liverpool Wavertree constituency party, Momentum members were demanding that Berger apologise for ever having opposed Corbyn and outlining how they hope to control her activities in Parliament: “She will now have to sit round the table with us the next time she wants to vote for bombing in Syria or to pass a no confidence motion in the leader of the party – she will have to be answerable to us.”

For her part, Berger has since “rushed out a statement” about how keen she is to see Labour elected and Corbyn installed in Downing Street.

It’s not yet clear to what extent this augers a realistic threat of a purge: previously Corbynites have found their legion of fans easier to mobilise for leadership elections than the dull, drawn-out process of institutional capture at which dedicated hard-leftists tend to excel.

Nonetheless, it’s a clear statement of intent on the part of Momentum and there will doubtless be further attempts. My colleague Mark Wallace found this list of MPs who should “join the Liberals”, including Berger, on a Momentum Facebook page.

All this makes the big question facing non-Corbynite Labour MPs (again, a large majority) more acute: how long can they justify lying down and collaborating with this project?

Since the election there has been a scramble amongst the Parliamentary Labour Party (PLP) to get into their leader’s good graces. But this strategy is surely unsustainable, as it involves ignoring both the reasons beyond electability which make Corbyn so unpalatable and the ongoing behaviour of his faction.

If there is another election, Labour could well win: there are sufficient marginals now that it would only take a small swing to put them over the top. Are the PLP actually ready to collaborate with the hard left’s programme for government? A programme that many of them deeply disagree with, but on which they would have been elected?

And if the Government lasts the course to 2019 or later, are they going to sit tight as Momentum gathers its forces in their constituency parties? Are they going to keep their heads down, either to hold onto their MP’s salary or in hope of a Shadow Cabinet post, as their colleagues are picked off one by one?

Tribal loyalty is a potent thing. It’s very difficult not to be gladdened when your team wins – or in Labour’s case, avoids a catastrophic defeat. But those Labour MPs who previously hoped for a Tory landslide that would discredit their leader must realise that their position has been worsened, not improved, by his apparent vindication last month.