The Brexit referendum results may have been illegally manipulated by online ads bought by the Vote Leave group in 2016. That's what Cambridge Analytica whistleblower Christopher Wylie told the British Parliament on Tuesday.

Wylie made the comments during questioning about Facebook by the Digital, Culture, Media and Sport Committee. Vote Leave group officials have denied breaking election rules and said they were facing an attempt to undermine Brexit by smearing their reputations. Wylie testified that former Vote Leave director Dominic Cummings admitted to have spent 40 percent of the group's budget on Canadian data company Aggregate IQ. The company put out "incredibly effective" online advertising to convert people's attitude toward leaving the European Union.