Daniel Hannan is an MEP for South-East England, and a journalist, author and broadcaster. His most recent book is How we invented Freedom and why it matters.

Amjad Bashir wants Britain to leave the EU, and has reached the view that the best way to make this happen is to secure a majority in the Commons for an In/Out referendum. A successful and patriotic businessman, he stood in UKIP’s interest at last year’s European election, but has since concluded that that party is, paradoxically, making withdrawal harder to achieve.

Now you can agree or disagree with his assessment. I happen to agree, but there are decent and sincere people who take a different view. That, though, isn’t the argument we’re hearing.

Instead, on discovering that he was leaving, UKIP suddenly announced that Bashir was under investigation, and tried to suggest that he would have been pushed had he not jumped. A week ago, the Yorkshireman was a popular frontbencher, often to be found in TV studios defending UKIP against accusations of bigotry. Now, the activists who were lauding him are trying to imply that he is some sort of crook.

Nothing in British politics is so ugly as the tribalism engendered by a defection. One moment, you’re cheering a fellow to the rafters; the next, you’re calling him a treacherous swine. Not because he has changed his opinions, his behaviour or his character, but simply because he has changed the colour of his rosette.

Calling defectors “unprincipled” is especially odd. Staying with your party is almost always the easier option. Defectors generally wrestle long and hard with their consciences, knowing that they will lose friends and disappoint people whose goodwill they value. Some of our greatest parliamentarians switched party because their convictions no longer accorded with their colleagues’: Castlereagh, Peel, Gladstone, Joe Chamberlain, Winston Churchill (twice).

Today, we regard these men as titans; but the parties they abandoned behaved in the same idiotic way that ours did over Mark Reckless, or that UKIP is now doing over Amjad Bashir.

Shall I tell you something? Accusations of treachery never work. Voters see them for what they are: sour grapes. Worse, such complaints turn politics into something like a local football derby: a random, irrational feud between people who, in other contexts, would get on perfectly well.

Seventy-four per cent of Conservative party members, according to a ConservativeHome survey, want a free-trade-only relationship with the EU. In the event that we secure a referendum, most of us will be campaigning alongside UKIP to shuffle off the dead coil of the EU and rediscover our global vocation. Amjad Bashir will, one assumes, be there with us. Do try to remember that, my UKIP friends.