PARIS — Hervé Falciani, a former Swiss bank employee who sparked an uproar across Europe by revealing formerly secret account information about tax evaders, is assuming a new role as an anticorruption adviser to a fledgling political party in Spain.

On Tuesday, Mr. Falciani — who took refuge in France earlier this year to evade criminal charges in Switzerland — and others kicked off the start of an anticorruption wing of Partido X, Spain’s newest political party.

Since Partido X was registered last December, it has been criticized for insisting on the anonymity of its members, who communicate largely through the Internet. The party argued that it wanted to avoid creating a cult of personalities, but this weekend it revealed the participation of Mr. Falciani as an adviser with an outsize, global profile.

Mr. Falciani, a former systems engineer, has wreaked havoc within the banking universe since 2008, when he amassed secret information while working at HSBC in Geneva about bank accounts at the core of the so-called Lagarde list, which roiled Greek politics with revelations of oligarchs and politicians who avoided taxes.