Because of the amount of corruption involved, it's hard not to be utterly cynical about Spanish politics. It therefore comes as no surprise that the dirty spotlight has been turned on Vox this week. Spain's over-worked anti-corruption prosecutor is looking into allegations made by the Socialists that the right-wing party has benefited from illegal financing.

The PSOE claims that, since at least 2020, Vox has collected around 5 million euros from donation boxes and the sale of merchandise on street stands, both of which violate funding regulations. The Socialists have also flagged a 6.5-million-euro loan, allegedly given to Vox by a Hungarian bank with connections to the country's right wing prime minister, Viktor Orban (also illegal).

The Socialists, you'll notice, took it upon themselves to investigate Vox. In any other European country - apart from Italy, perhaps - that would be highly unusual. Rifling through political parties' financial records is usually thought of as a job for lawyers, judges and police officers, not politicians. Politicians are too busy creating and critiquing policy to conduct investigations into their opponents' funding practices. That is not what they're paid or elected to do. They are paid to represent the people who voted for them.

You are no doubt - and quite rightly - boggling at my naivety. In Spain, corruption allegations are the fuel on which politics runs.

Imagine, if you will, a large, well-staffed office in the Socialists' HQ, the sole purpose of which is to prove that Vox is corrupt. Interns are sent out to rummage through the party's bins; its members' phones are tapped, a tactic which the PSOE allegedly also used against Catalan separatists; and their cars are followed, in the hope that they'll rock up to a flashing roadside 'nightclub', or the bugged offices of a corrupt cop.

Halfway through their first week, one of the interns asks their supervisor, a veteran Socialist, an embarrassing question: "Wait, shouldn't we be concentrating on policies? Isn't that what politics is about?" The room falls silent for a few seconds. Then everyone bursts out laughing. It's quite some time before people return to work, wiping tears from their eyes. "Policies!" says the veteran Socialist under his breath, shaking his head and chuckling.

It can be no coincidence, surely, that the Socialists launched their investigation into Vox at a time when they are also under suspicion of corruption, in the so-called Koldo case. The PSOE, like the PP, is not in a position to criticise anyone for dodgy practices; and Vox won't be either, if it's found guilty. But if none of the main parties in Spain is able to make corruption allegations against its enemies, political discourse will effectively cease.