Leave campaigners have found themselves facing questions over £600,000 of donations they reportedly accepted from a former member of the British National Party.
Electoral Commission figures released yesterday show Sutton Coldfield resident Gladys Bramall as Vote Leave's third largest individual donor.
The 88-year-old made two separate donations of £500,000 and £100,000.
However, Buzzfeed News reported that Bramall was listed on a leaked BNP membership list.
Bramall told Buzzfeed that she had been unknowingly signed up to party membership by her husband.
Pressed on the revelations, Vote Leave's Michael Gove responded on LBC that money from "tainted sources" would play no part in the campaign.
Remain backer Sam Gyimah MP described the findings as "extremely concerning".