The other day I sat talking to a Labour MP, someone for whom I have the greatest of respect. And they told me that they got up every morning feeling terrible. They spoke out against antisemitism in the party, and received a good deal of coverage as a dissenting MP, but they were no longer sure if they were being brave or being a coward.

And I was reassuring. I told them they were being brave and I really think that. I am very sympathetic to the plight of MPs who feel that they shouldn’t be driven out of their own party because they are Jewish or hate antisemitism.

For myself, I couldn’t be a member of such a party and I couldn’t vote for it, but that is really easy for me to say. So I was reassuring. Up to a point.

But now, hear me out and follow my logic.

The truth is that this is a problem that isn’t going away. And so it is no longer enough to be concerned about it and hope that it will resolve itself. It will not resolve itself.

What moderate MPs, concerned about anti-semitism, need is a strategy. I think they are drifting and putting off hard decisions because they are too hard. In what follows I just want to be as simple, straightforward and hard-headed as possible.

Let’s use the advice of game theorists about strategic thinking — think forward and reason backwards. Decide where you want to be eventually and start doing now the things you will need in order to be in the place you want later.

MPs need to ask themselves whether, in the absence of a profound change of doctrine or character or kitchen cabinet, they are willing to support Jeremy Corbyn as prime minister in a general election.

For most of the MPs in question the answer seems to be no, yet they have no strategy for avoiding this. The danger is that because they are not thinking forward and reasoning backwards they will one day find themselves doing exactly what they promise today they would not.

So what would you do today if you wanted to be in the position of not supporting Mr Corbyn as prime minister come election time? One of four things. Remove Mr Corbyn as leader of the party; leave the party; stay in the party but don’t run for parliament or stay in the party and try your best to make sure it doesn’t provide the prime minister.

(There is of course a fourth option, which is to allow Mr Corbyn to be prime minister but assume that he can be controlled from parliament to such an extent that it hardly matters what he thinks. This is comforting but delusional).

I don’t think it is at all likely that Mr Corbyn will be removed as leader of the Labour Party. His general performance makes it possible but only remotely. Which only leaves the other three options.

Here’s the next thing. There could be a general election within weeks. So MPs who want to be certain that they won’t find themselves supporting Mr Corbyn as prime minister at the next election have to start down one of the available paths now.

Retiring at the next election doesn’t require much planning, so no action need be taken right away. But that only leaves the other two paths, and if the MP doesn’t go down either of those they may find retirement their only option if there is an election called soon. If they want to avoid having, in a hurry, to choose between supporting Mr Corbyn and retirement, they need to plan.

The route of leaving the party involves organising a new party or joining an existing one. So they either have to start positioning themselves to join the Lib Dems or start establishing a national membership network of an entirely new structure.

The route of staying in the party but effectively aiding its opponents requires the MPs to lead dissent. It involves clever drawing of political lines, readying local parties to sustain their dissident position and establishing clear arguments. And that has to start now too.

And why am I saying all this? Because if you see how difficult it is, and realise how bold the action required is, and how soon it has to be taken you end up thinking…mmmm, these people aren’t going to do anything, are they?

Daniel Finkelstein is Associate Editor of The Times and a Conservative Peer