A mysterious pro-Brexit campaign group has spent more than any other organization on political ads in the United Kingdom on Facebook, since the social media giant began publishing spending data in October.

Britain's Future, which has never disclosed the source of its finances or organizational structure, has raised concerns about the source of funding in British politics.

The campaign group has spent more than 340,000 pounds ($442,000) on Facebook adverts backing a hard Brexit since the data tracking began last year, making it a bigger spender than every UK political party and the government combined.

However, there is no information available about who is ultimately paying for the adverts, highlighting a key flaw in Facebook's new political transparency tools.

Britain's Future's public presence contains links to just two individuals: Tim Dawson, a screenwriter and journalist, and, indirectly, a former British National Party (BNP) candidate, Colin Banner, who has denied any involvement.

Dawson stood for election to Manchester city council as a Conservative candidate before last year becoming the public face of Britain's Future.

The campaign group has spent the money on targeted Facebook and Instagram adverts in just a few months, including more than 50,000 pounds last week alone, urging voters to email their local member of Parliament and tell them to get Britain out of the European Union.

There's no suggestion Britain's Future has broken any rules. Under the UK's electoral system, third parties who want to campaign during referendums and elections have to register with the Electoral Commission and provide details of their spending and donors. Those records are made public. But these rules don't apply outside of official campaign periods.

Britain's Future is not a political party and does not appear to have any intention of putting forward candidates in elections, so is not regulated by laws requiring large political donations to be publicly declared.

Last month, a report from the Department for Digital, Culture, Media and Sport warned that electoral law was out of date and vulnerable to manipulation by hostile forces, and that the need to update it was urgent.

In October, Facebook launched a searchable archive of the political ads running on its platform in the UK and began publishing weekly data on the top political spenders, though there is no equivalent database for Google, Twitter or other online advertisers.

"I've been pretty astonished, actually, about how little movement there's been around electoral law reform in the last couple of years," Martin Moore, director of the Centre for the Study of Media, Communication and Power at King's College London, told BuzzFeed News. "Even the basic stuff hasn't been tackled."

Contact the writer at jonathan@mail.chinadailyuk.com