A controversial Madrid-based campaign group, supported by American and Russian ultra-conservatives, is working across Europe to drive voters towards far-right parties in next month’s European Parliament elections and in Spain’s national elections this Sunday, openDemocracy can reveal today.

Our findings have caused alarm among lawmakers who fear that Trump-linked conservatives are working with European allies to import a controversial US-style ‘Super PAC’ model of political campaigning to Europe – opening the door to large amounts of ‘dark money’ flowing unchecked into elections and referenda.

The Madrid-based campaign group CitizenGo is best known for its online petitions against same-sex marriage, sex education and abortion – and for driving buses across cities with slogans against LGBT rights and “feminazis”.

But now openDemocracy can reveal new evidence of what a group of MEPs has called “deeply concerning" coordination between this group and far-right parties across Europe – from Spain to Italy, Germany and Hungary.

In Spain, CitizenGo is supporting the far-right party Vox that is expected to make big gains this weekend, winning seats in the country’s parliament for the first time and potentially forming part of the new government.

Speaking to our undercover reporter posing as a potential donor, CitizenGo’s director described plans to run attack ads against Vox’s political opponents, and talked about how to get around campaign finance laws.

Meanwhile a senior Vox official compared CitizenGo to a “Super PAC” in the US, referring to the controversial groups that can spend unlimited sums influencing elections in America – and which are known for aggressive, negative campaigning.

openDemocracy can further reveal today how CitizenGo has been supported by an experienced American political fundraiser and tech consultant linked to the Trump campaign, the Republican Party and the Tea Party movement, who boasted of being able to use controversial technology to collect personal data about potential voters.

Former US Democratic Senator Russ Feingold described our findings as “frightening” and called on European leaders to act to protect the democratic process.

“Europe has an opportunity to get ahead of this and not make the same mistakes that were made here in the United States”, said Feingold, who worked alongside Republican senator John McCain for reform of electoral finance in the US.

CitizenGo’s board also includes a close business associate of the “Orthodox Oligarch” Konstantin Malofeev – who has been targeted by US and European sanctions for allegedly propping up the pro-Russian breakaway republic in eastern Ukraine – and an Italian politician, Luca Volonte, currently on trial in Milan facing corruption charges.

European lawmakers have described openDemocracy’s findings as “explosive” and have called for “urgent action” to “maintain the integrity” of upcoming elections.

In a letter to the European Commission’s transparency tsar Frans Timmermans, MPs, MEPs and Senators from six European countries said these findings “merit urgent and high level investigation by the European Commission and relevant national authorities”.

“We have all seen how democracy can easily be eroded if we remain complacent about the activities of anti-democratic actors… [who oppose] European fundamental rights, European values and liberal democracy”, they warned.