LONDON (AP) — A group of whistleblowers are questioning the integrity of Britain's vote to leave the European Union, presenting 50 pages of documents that they say prove the official Brexit campaign group violated election finance rules on the way to winning the 2016 referendum.

The trio, which includes the man who triggered concerns about the misuse of Facebook data during the U.S. presidential election, alleges that the official Vote Leave campaign circumvented spending limits by funneling 625,000 pounds ($888,000) to another group called BeLeave.

The most prominent among them, Chris Wylie, says "this is not about re-fighting the referendum. It's about the integrity of the democratic process."

The documents included electronic message exchanges, Google document shots and photographs.

Vote Leave denies it broke any campaign rules.