The Tory defectors strengthen the Independent Group, but will have no impact on Brexit – here's why

The Tory breakaway is remarkably similar to the Labour one in that its cause is something that happened some time ago

The defection of three Conservative MPs is prompted by the imminent crunch of leaving the EU, but it seems unlikely to affect the course of Brexit. The main effect is to strengthen the claim of the proto-party of the Independent Group to represent a broad swathe of opinion across the spectrum.

Heidi Allen, Anna Soubry and Sarah Wollaston were already strongly opposed to Brexit and want a second referendum to try to stay in the EU, as are all the ex-Labour members of the 11-strong Independent Group. From the joint letter of resignation by the three Tories, it seems that the threat of a no-deal Brexit was what finally tipped them over the brink.

But they were already winning that battle. There are many ministers, including several cabinet ministers, who are already threatening to resign – from the government rather than from the party – if Theresa May tries to go ahead with leaving the EU without a deal. So what happens if we leave the EU with a deal, or if Brexit is postponed thanks to the cross-party effort led by Yvette Cooper?

Then we have to read further down the resignation letter to establish that the three have a bigger problem with “a shift to the right of British politics”. They say they cannot remain in a party “so firmly in the grip of the ERG and DUP”. But this seems only to restate their objection to Brexit in a different way. No one suggests the Tory government has been influenced by the DUP’s attitudes on gay rights or abortion, so it can only be the Northern Ireland party’s opposition to the prime minister’s Brexit deal that the defectors don’t like.

As for the ERG – the European Research Group of Eurosceptic Tory MPs – they have been operating as a party within a party for some time. Hence the Tory breakaway is remarkably similar to the Labour one in that its cause is something that happened some time ago – in the Labour case it was the election of Jeremy Corbyn as leader three and a half years ago.

But neither set of defections changes the balance of forces in the House of Commons on the question of Brexit. The supporters of a new referendum remain in a minority, and with no prospect of winning a majority unless Corbyn himself whips Labour MPs for it.

Yet the Labour breakaway may well have made it less likely that the Labour leader will back a referendum. He made a small gesture in that direction in his email to members after the launch of the Independent Group, by graciously mentioning the Labour policy of keeping “a public vote” on the table, and he may continue to sound warmer about a referendum in an attempt to discourage other MPs from defecting. But he always seems to find it hard to suppress his real view, which seems to be that he wants to leave the EU as long as no one can blame him for it.

So what will happen after Britain has either left the EU or its departure has been postponed for a few months? Then the true significance of today’s defections is that it makes the Labour defectors stronger. Or, at least, it might strengthen them in the eyes of the general public. It makes their embryo party more attractive to swing voters whose party loyalties are weak. But it weakens their appeal to many mainstream Labour supporters. Many of them may have their differences with Corbyn, but would hesitate to join something that substantiates the Corbynite attack on them as closet Tories.

Today’s defections will put to the test the conventional wisdom of the Blair era that elections are won and lost in the centre ground. Everyone knows that the Social Democratic Party crashed and burned electorally, but it is less often remarked that the shock the SDP administered to the system forced the Labour Party especially to change, although it took a long time for that change to work through.