To avoid a hard Brexit, you may have to choose a party you never dreamed of voting for

It makes sense to back pro-Remain Conservatives. In a Tory-dominated House of Commons, one of the few brakes on a destructive Brexit will be people within the Prime Minister's own party who are prepared to challenge her

Choosing a candidate who opposes Brexit and Article 50 will be tough for many voters (Getty)

Imagine you are worried about a destructive Brexit. One that would damage the economy, undermine our influence in the world and possibly tear the country itself apart. And you think such an outcome is more likely if Theresa May emerges on 9 June with untrammelled power.

The Prime Minister is bad at consulting at the best of times, as we’ve seen with her dementia tax. Think what she’d be like if she wins the election with a three-digit majority.

How should you vote?

Easy, you might say. Labour.

Not so fast. For a start, Jeremy Corbyn’s policy on Brexit hasn’t been great. He has failed to provide any real opposition to the Tories. He has decided to quit the single market, meaning he too would damage the economy. And he won’t let the people vote on whether they still want to quit the EU when they finally know what Brexit means.

Sure, Corbyn says he won’t crash out with no deal – something May and her cabinet ministers threaten every other day. So Labour’s policy is definitely better than the Conservatives’. But there’s another factor to take account of: Labour is going to struggle to hang onto the seats it has got, let alone win any more.

What about the Liberal Democrats or the Greens, then? They have good Brexit policies. They want Britain to stay in the single market. They are also promising the people a referendum on the final deal. So where either party has a chance of winning, it makes sense to back them. The snag is that, even if one is being optimistic, there are only a few dozen seats where that’s the case.

Vote tactically then. Simply back the candidate which has the best chance of beating the Tories wherever you live. Isn’t that the solution?

Well, yes and no. If there’s a chance of kicking out a Tory Brexiteer, go for it. But there are three problems with this simple rule.

First, some Conservative candidates have been prepared to stick their neck out and oppose Theresa May’s Brexit policies. Not many, it must be admitted. Most of those who campaigned for Remain during the referendum are now toeing the party line.

But some, such as Nick Herbert, defied May’s whips and abstained in the Article 50 vote. Kenneth Clarke even voted against triggering Article 50. Others, such as Nicky Morgan and Anna Soubry, fought for Parliament to get a meaningful vote on the final Brexit deal – again flouting the Prime Minister’s will.

It makes sense to back these Conservatives. In a Tory-dominated House of Commons, one of the few brakes on a destructive Brexit will be people within the Prime Minister’s own party who are prepared to challenge her.

Another problem with the simple anti-Tory tactical voting rule is that there are vast swathes of the country where there’s no chance of removing them. In most of these seats, Labour is second. But tactical voting is pointless because it won’t change anything.

A better approach in these constituencies is to vote for one of the genuinely pro-European parties - the Greens or Lib Dems. That, of course, won’t change who is the MP either. But at least it will boost these parties’ share of the national vote, giving them a stronger platform from which to oppose a destructive Brexit. In these seats, a vote for Corbyn’s Labour is a wasted one.

The final problem with the simple anti-Tory voting rule is that it doesn’t say what you should do if Labour is defending a seat. Easy, you might say, back them.

But, again, not so fast. For a start, there are nine Labour Brexiteers, standing for re-election. Almost all are in safe seats. But even so, it is surely better to register a protest vote by supporting a genuinely pro-European party. And in Vauxhall, where Kate Hoey is facing a stiff challenge from a Lib Dem, those opposed to a destructive Brexit should rally around him.

What’s more, there are quite a few safe Labour seats where the candidate voted Remain during the referendum but is now going along with Corbyn’s spineless Europe policy. Going meekly into the polling booth and putting one’s cross against their names won’t do anything to stop a destructive Brexit.

The better approach, again, is to back the Greens or Lib Dems. They won’t have a chance of winning. But voting for them won’t put these safe Labour candidates at risk either. What it will do is boost the national share of the genuinely pro-European parties – and that is worthwhile.

Of course, voters should always support Labour MPs who continued to fight a destructive Brexit since the referendum – say by rebelling against Corbyn’s edict that they should vote in favour of triggering Article 50. And they should ride to the rescue of any Labour MPs who are under threat from the Tories. But otherwise, people should vote for a party they really believe in.

So what is one left with? A fairly complex situation, with the best party to back depending on the parties’ positions, the candidates’ views and the seat’s win-ability.

InFacts, the journalistic website I edit, has produced an interactive guide that applies these principles to all the constituencies in England and Wales. It’s not a black box as in each case we give reasons for our recommendations.

Those looking for a magic formula to wish away last year’s referendum result won’t find what they are looking for. But it will appeal to those who want to stop a destructive Brexit and are determined to make their votes count. This might involve voting for a party you have never imagined voting for previously. It would be worth it.

Hugo Dixon is editor-in-chief of InFacts